The Experts below are selected from a list of 5433 Experts worldwide ranked by ideXlab platform

Janusz J. Zwiazek - One of the best experts on this subject based on the ideXlab platform.

  • Diurnal and seasonal changes of Leaf Lamina hydraulic conductance in bur oak (Quercus macrocarpa) and trembling aspen (Populus tremuloides)
    Trees, 2010
    Co-Authors: Mihaela C. Voicu, Janusz J. Zwiazek
    Abstract:

    The aim of this study was to examine the diurnal and seasonal variations in the sensitivity of Leaf Lamina (Klam) hydraulic conductance to irradiance in bur oak (Quercus macrocarpa Michx.) and trembling aspen (Populus tremuloides Michx.), which vary in their responses of Klam to irradiance. Klam was determined using the high-pressure method and the measurements were carried out in June, August and September. The irradiance response of Klam in bur oak was present throughout the day and declined in senescing leaves. In trembling aspen, Klam declined from morning to late afternoon and drastically decreased before the onset of Leaf senescence, but it was not sensitive to irradiance. In both tree species, the capacity of the petioles to supply water to Leaf Lamina changed during the day in accordance with the ability of the Leaf Lamina to transport water. Petiole hydraulic conductivity (Kpet) declined during the season in bur oak leaves, while it tended to increase in trembling aspen leaves. There was no correlation between the Klam values and air temperature or light intensity at the time of Leaf collection. For trembling aspen, Kpet was negatively correlated with the air temperature suggesting sensitivity to drought. We conclude that the water transport properties of petioles and Leaf Lamina in the two studied tree species reflect their ecological adaptations. Trembling aspen leaves have high hydraulic conductivity and high stomatal conductance regardless of the irradiance level, consistent with the rapid growth and high demand for water. In contrast, the increased Lamina hydraulic conductivity and stomatal conductance under high irradiance in bur oak trees reflect a water conservation strategy.

  • Inhibitor studies of Leaf Lamina hydraulic conductance in trembling aspen (Populus tremuloides Michx.) leaves.
    Tree physiology, 2009
    Co-Authors: Mihaela C. Voicu, Janusz J. Zwiazek
    Abstract:

    Summary The present study investigated Leaf water transport properties in trembling aspen (Populus tremuloides) leaves. Leaf Lamina hydraulic conductance (Klam) and stomatal conductance (gs) were drastically suppressed by NaF (a general metabolic inhibitor). In leaves treated with 0.2 mM HgCl2 (an aquaporin blocker), Klam declined by 22% when the leaves were sampled in June but the decline was not significant when the leaves were sampled in August. The leaves sampled in June that transpired 30 mM β-mercaptoethanol following mercury application showed similar Klam as those in control leaves transpiring distilled water. When leaves were pressure-infiltrated with 0.1 mM HgCl2, Klam significantly declined by 25%. Atrazine (a photosystem II inhibitor) drastically reduced Leaf net CO2 uptake by the leaves from seedlings and mature trees but did not have any effect on Klam regardless of the irradiance at the Leaf level during the Klam measurements. When PTS3 (trisodium 3-hydroxy-5,8,10-pyrenetrisulphonate) apoplastic tracer was pressure-infiltrated inside the leaves, its concentration in the Leaf exudates did not change from ambient light to high irradiance treatment and declined in the presence of HgCl2 in the treatment solution. Trembling aspen Klam appears to be linked to Leaf metabolism and is uncoupled from the short-term variations in photosynthesis. Aquaporin-mediated water transport does not appear to constitute the dominant pathway for the pressure-driven water flow in the leaves of trembling aspen trees.

Chiyoko Machida - One of the best experts on this subject based on the ideXlab platform.

  • Formation of a Symmetric Flat Leaf Lamina in Arabidopsis
    Morphogenesis and Pattern Formation in Biological Systems, 2003
    Co-Authors: Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Endang Semiarti, Hirokazu Tsukaya, Mitsuyasu Hasebe, Shoko Kojima, Yasunori Machida
    Abstract:

    The ASYMMETRIC LEAVESI (AS1) and ASYMMETRIC LEAVES2 (AS2) genes of Arabidopsis thatiana are involved in the establishment of the Leaf venation system, which includes the prominent midvein, as well as in the development of a symmetric Lamina. The gene product also represses the expression of class 1 knox homeobox genes in leaves. We have characterized the AS2 gene, which appears to encode a novel protein with cysteine repeats (designated the C-motif), conserved glycine, and a leucine-zipper-like sequence in the amino-terminal half of the primary sequence. The Arabidopsis genome contains 42 putative genes that potentially encode proteins with conserved amino acid sequences in the amino-terminal half. Thus, the AS2 protein belongs to a novel family of proteins that we have designated the AS2 family. Members of this family except AS2 also have been designated ASLs (AS2-like proteins). Overexpression of AS2 cDNA in transgenic Arabidopsis plants resulted in upwardly curled leaves, which differed markedly from the downwardly curled leaves generated by loss-of-function mutation of AS2. Our results suggest that AS2 functions in the transcription of a certain gene(s) in plant nuclei and thereby controls the formation of a symmetric flat Leaf Lamina and the establishment of a prominent midvein and other patterns of venation.

  • The ASYMMETRIC LEAVES2 gene of Arabidopsis thaliana, required for formation of a symmetric flat Leaf Lamina, encodes a member of a novel family of proteins characterized by cysteine repeats and a leucine zipper.
    Plant & cell physiology, 2002
    Co-Authors: Hidekazu Iwakawa, Yoshihisa Ueno, Endang Semiarti, Hirokazu Tsukaya, Mitsuyasu Hasebe, Shoko Kojima, Hitoshi Onouchi, Teppei Soma, Masaya Ikezaki, Chiyoko Machida
    Abstract:

    The ASYMMETRIC LEAVES2 (AS2) gene of Arabidopsis thaliana is involved in the establishment of the Leaf venation system, which includes the prominent midvein, as well as in the development of a symmetric Lamina. The gene product also represses the expression of class 1 knox homeobox genes in leaves. We have characterized the AS2 gene, which appears to encode a novel protein with cysteine repeats (designated the C-motif) and a leucine-zipper-like sequence in the amino-terminal half of the primary sequence. The Arabidopsis genome contains 42 putative genes that potentially encode proteins with conserved amino acid sequences that include the C-motif and the leucine-zipper-like sequence in the amino-terminal half. Thus, the AS2 protein belongs to a novel family of proteins that we have designated the AS2 family. Members of this family except AS2 also have been designated ASLs (AS2-like proteins). Transcripts of AS2 were detected mainly in adaxial domains of cotyledonary primordia. Green fluorescent protein-fused AS2 was concentrated in plant cell nuclei. Overexpression of AS2 cDNA in transgenic Arabidopsis plants resulted in upwardly curled leaves, which differed markedly from the downwardly curled leaves generated by loss-of-function mutation of AS2. Our results suggest that AS2 functions in the transcription of a certain gene(s) in plant nuclei and thereby controls the formation of a symmetric flat Leaf Lamina and the establishment of a prominent midvein and other patterns of venation.

  • the asymmetric leaves2 gene of arabidopsis thaliana regulates formation of a symmetric Lamina establishment of venation and repression of meristem related homeobox genes in leaves
    Development, 2001
    Co-Authors: Endang Semiarti, Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Hirokazu Tsukaya, Yasunori Machida
    Abstract:

    The asymmetric leaves2 (as2) mutant of Arabidopsis thaliana generated Leaf lobes and Leaflet-like structures from the petioles of leaves in a bilaterally asymmetric manner. Both the delayed formation of the primary vein and the asymmetric formation of secondary veins were apparent in Leaf primordia of as2 plants. A distinct midvein, which is the thickest vein and is located in the longitudinal center of the Leaf Lamina of wild-type plants, was often rudimentary even in mature as2 leaves. However, several parallel veins of very similar thickness were evident in such leaves. The complexity of venation patterns in all Leaf-like organs of as2 plants was reduced. The malformed veins were visible before the development of asymmetry of the Leaf Lamina and were maintained in mature as2 leaves. In vitro culture on phytohormone-free medium of Leaf sections from as2 mutants and from the asymmetric leaves1 (as1) mutant, which has a phenotype similar to that of as2, revealed an elevated potential in both cases for regeneration of shoots from Leaf cells. Analysis by the reverse transcription-polymerase chain reaction showed that transcripts of the KNAT1, KNAT2 and KNAT6 (a recently identified member of the class 1 knox family) genes accumulated in the leaves of both as2 and as1 plants but not of wild type. Transcripts of the STM gene also accumulated in as1 leaves. These findings suggest that, in leaves, the AS2 and AS1 genes repress the expression of these homeobox genes, which are thought to maintain the indeterminate cell state in the shoot apical meristem. Taken together, our results suggest that AS2 and AS1 might be involved in establishment of a prominent midvein and of networks of other veins as well as in the formation of the symmetric Leaf Lamina, which might be related to repression of class 1 knox homeobox genes in leaves.

  • The Asymmetric Leaves2 (AS2) Gene of Arabidopsis Thaliana Regulates Lamina Formation and is Required for Patterning of Leaf Venation
    Progress in Biotechnology, 2001
    Co-Authors: Endang Semiarti, Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Hirokazu Tsukaya, Yasunori Machida
    Abstract:

    ABSTRACT To understand the molecular mechanisms behind symmetrical development of Leaf, we have analyzed the asymmetric leaves2 (as2) mutant of A. thaliana, which generated Leaf lobes and Leaflet-like structures from the petioles of leaves in a bilaterally asymmetric manner. The delayed formation of the primary vein and the asymmetric formation of secondary veins were apparent in Leaf primordia of as2 plants. A distinct midvein, which is the thickest vein and is located in the longitudinal center of the Leaf Lamina of wild-type plants, was often rudimentary even in mature as2 leaves. However, several parallel veins of very similar thickness were evident in such leaves. The malformed veins were visible prior to the development of asymmetry of the Leaf Lamina, and were maintained in the mature as2 leaves. Culture in vitro on phytohormone-free medium of Leaf sections from the as2 mutants and from the asymmetric leavesl (as1) mutant, which has a phenotype similar to that of as2, revealed an elevated potential in both cases for regeneration of shoots from Leaf cells. Analysis by the reverse transcription-polymerase chain reaction showed that AS2 and AS1 negatively regulates the homeobox genes KNAT1, KNAT2 and KNAT6 in leaves. Taken together, our results suggest that AS2 and AS1 are involved in establishment of Leaf venation and the formation of symmetric Leaf Lamina, which might be related to repression of expression of the homeobox genes in leaves.

Mihaela C. Voicu - One of the best experts on this subject based on the ideXlab platform.

  • Diurnal and seasonal changes of Leaf Lamina hydraulic conductance in bur oak (Quercus macrocarpa) and trembling aspen (Populus tremuloides)
    Trees, 2010
    Co-Authors: Mihaela C. Voicu, Janusz J. Zwiazek
    Abstract:

    The aim of this study was to examine the diurnal and seasonal variations in the sensitivity of Leaf Lamina (Klam) hydraulic conductance to irradiance in bur oak (Quercus macrocarpa Michx.) and trembling aspen (Populus tremuloides Michx.), which vary in their responses of Klam to irradiance. Klam was determined using the high-pressure method and the measurements were carried out in June, August and September. The irradiance response of Klam in bur oak was present throughout the day and declined in senescing leaves. In trembling aspen, Klam declined from morning to late afternoon and drastically decreased before the onset of Leaf senescence, but it was not sensitive to irradiance. In both tree species, the capacity of the petioles to supply water to Leaf Lamina changed during the day in accordance with the ability of the Leaf Lamina to transport water. Petiole hydraulic conductivity (Kpet) declined during the season in bur oak leaves, while it tended to increase in trembling aspen leaves. There was no correlation between the Klam values and air temperature or light intensity at the time of Leaf collection. For trembling aspen, Kpet was negatively correlated with the air temperature suggesting sensitivity to drought. We conclude that the water transport properties of petioles and Leaf Lamina in the two studied tree species reflect their ecological adaptations. Trembling aspen leaves have high hydraulic conductivity and high stomatal conductance regardless of the irradiance level, consistent with the rapid growth and high demand for water. In contrast, the increased Lamina hydraulic conductivity and stomatal conductance under high irradiance in bur oak trees reflect a water conservation strategy.

  • Inhibitor studies of Leaf Lamina hydraulic conductance in trembling aspen (Populus tremuloides Michx.) leaves.
    Tree physiology, 2009
    Co-Authors: Mihaela C. Voicu, Janusz J. Zwiazek
    Abstract:

    Summary The present study investigated Leaf water transport properties in trembling aspen (Populus tremuloides) leaves. Leaf Lamina hydraulic conductance (Klam) and stomatal conductance (gs) were drastically suppressed by NaF (a general metabolic inhibitor). In leaves treated with 0.2 mM HgCl2 (an aquaporin blocker), Klam declined by 22% when the leaves were sampled in June but the decline was not significant when the leaves were sampled in August. The leaves sampled in June that transpired 30 mM β-mercaptoethanol following mercury application showed similar Klam as those in control leaves transpiring distilled water. When leaves were pressure-infiltrated with 0.1 mM HgCl2, Klam significantly declined by 25%. Atrazine (a photosystem II inhibitor) drastically reduced Leaf net CO2 uptake by the leaves from seedlings and mature trees but did not have any effect on Klam regardless of the irradiance at the Leaf level during the Klam measurements. When PTS3 (trisodium 3-hydroxy-5,8,10-pyrenetrisulphonate) apoplastic tracer was pressure-infiltrated inside the leaves, its concentration in the Leaf exudates did not change from ambient light to high irradiance treatment and declined in the presence of HgCl2 in the treatment solution. Trembling aspen Klam appears to be linked to Leaf metabolism and is uncoupled from the short-term variations in photosynthesis. Aquaporin-mediated water transport does not appear to constitute the dominant pathway for the pressure-driven water flow in the leaves of trembling aspen trees.

Hidekazu Iwakawa - One of the best experts on this subject based on the ideXlab platform.

  • Formation of a Symmetric Flat Leaf Lamina in Arabidopsis
    Morphogenesis and Pattern Formation in Biological Systems, 2003
    Co-Authors: Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Endang Semiarti, Hirokazu Tsukaya, Mitsuyasu Hasebe, Shoko Kojima, Yasunori Machida
    Abstract:

    The ASYMMETRIC LEAVESI (AS1) and ASYMMETRIC LEAVES2 (AS2) genes of Arabidopsis thatiana are involved in the establishment of the Leaf venation system, which includes the prominent midvein, as well as in the development of a symmetric Lamina. The gene product also represses the expression of class 1 knox homeobox genes in leaves. We have characterized the AS2 gene, which appears to encode a novel protein with cysteine repeats (designated the C-motif), conserved glycine, and a leucine-zipper-like sequence in the amino-terminal half of the primary sequence. The Arabidopsis genome contains 42 putative genes that potentially encode proteins with conserved amino acid sequences in the amino-terminal half. Thus, the AS2 protein belongs to a novel family of proteins that we have designated the AS2 family. Members of this family except AS2 also have been designated ASLs (AS2-like proteins). Overexpression of AS2 cDNA in transgenic Arabidopsis plants resulted in upwardly curled leaves, which differed markedly from the downwardly curled leaves generated by loss-of-function mutation of AS2. Our results suggest that AS2 functions in the transcription of a certain gene(s) in plant nuclei and thereby controls the formation of a symmetric flat Leaf Lamina and the establishment of a prominent midvein and other patterns of venation.

  • The ASYMMETRIC LEAVES2 gene of Arabidopsis thaliana, required for formation of a symmetric flat Leaf Lamina, encodes a member of a novel family of proteins characterized by cysteine repeats and a leucine zipper.
    Plant & cell physiology, 2002
    Co-Authors: Hidekazu Iwakawa, Yoshihisa Ueno, Endang Semiarti, Hirokazu Tsukaya, Mitsuyasu Hasebe, Shoko Kojima, Hitoshi Onouchi, Teppei Soma, Masaya Ikezaki, Chiyoko Machida
    Abstract:

    The ASYMMETRIC LEAVES2 (AS2) gene of Arabidopsis thaliana is involved in the establishment of the Leaf venation system, which includes the prominent midvein, as well as in the development of a symmetric Lamina. The gene product also represses the expression of class 1 knox homeobox genes in leaves. We have characterized the AS2 gene, which appears to encode a novel protein with cysteine repeats (designated the C-motif) and a leucine-zipper-like sequence in the amino-terminal half of the primary sequence. The Arabidopsis genome contains 42 putative genes that potentially encode proteins with conserved amino acid sequences that include the C-motif and the leucine-zipper-like sequence in the amino-terminal half. Thus, the AS2 protein belongs to a novel family of proteins that we have designated the AS2 family. Members of this family except AS2 also have been designated ASLs (AS2-like proteins). Transcripts of AS2 were detected mainly in adaxial domains of cotyledonary primordia. Green fluorescent protein-fused AS2 was concentrated in plant cell nuclei. Overexpression of AS2 cDNA in transgenic Arabidopsis plants resulted in upwardly curled leaves, which differed markedly from the downwardly curled leaves generated by loss-of-function mutation of AS2. Our results suggest that AS2 functions in the transcription of a certain gene(s) in plant nuclei and thereby controls the formation of a symmetric flat Leaf Lamina and the establishment of a prominent midvein and other patterns of venation.

  • the asymmetric leaves2 gene of arabidopsis thaliana regulates formation of a symmetric Lamina establishment of venation and repression of meristem related homeobox genes in leaves
    Development, 2001
    Co-Authors: Endang Semiarti, Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Hirokazu Tsukaya, Yasunori Machida
    Abstract:

    The asymmetric leaves2 (as2) mutant of Arabidopsis thaliana generated Leaf lobes and Leaflet-like structures from the petioles of leaves in a bilaterally asymmetric manner. Both the delayed formation of the primary vein and the asymmetric formation of secondary veins were apparent in Leaf primordia of as2 plants. A distinct midvein, which is the thickest vein and is located in the longitudinal center of the Leaf Lamina of wild-type plants, was often rudimentary even in mature as2 leaves. However, several parallel veins of very similar thickness were evident in such leaves. The complexity of venation patterns in all Leaf-like organs of as2 plants was reduced. The malformed veins were visible before the development of asymmetry of the Leaf Lamina and were maintained in mature as2 leaves. In vitro culture on phytohormone-free medium of Leaf sections from as2 mutants and from the asymmetric leaves1 (as1) mutant, which has a phenotype similar to that of as2, revealed an elevated potential in both cases for regeneration of shoots from Leaf cells. Analysis by the reverse transcription-polymerase chain reaction showed that transcripts of the KNAT1, KNAT2 and KNAT6 (a recently identified member of the class 1 knox family) genes accumulated in the leaves of both as2 and as1 plants but not of wild type. Transcripts of the STM gene also accumulated in as1 leaves. These findings suggest that, in leaves, the AS2 and AS1 genes repress the expression of these homeobox genes, which are thought to maintain the indeterminate cell state in the shoot apical meristem. Taken together, our results suggest that AS2 and AS1 might be involved in establishment of a prominent midvein and of networks of other veins as well as in the formation of the symmetric Leaf Lamina, which might be related to repression of class 1 knox homeobox genes in leaves.

  • The Asymmetric Leaves2 (AS2) Gene of Arabidopsis Thaliana Regulates Lamina Formation and is Required for Patterning of Leaf Venation
    Progress in Biotechnology, 2001
    Co-Authors: Endang Semiarti, Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Hirokazu Tsukaya, Yasunori Machida
    Abstract:

    ABSTRACT To understand the molecular mechanisms behind symmetrical development of Leaf, we have analyzed the asymmetric leaves2 (as2) mutant of A. thaliana, which generated Leaf lobes and Leaflet-like structures from the petioles of leaves in a bilaterally asymmetric manner. The delayed formation of the primary vein and the asymmetric formation of secondary veins were apparent in Leaf primordia of as2 plants. A distinct midvein, which is the thickest vein and is located in the longitudinal center of the Leaf Lamina of wild-type plants, was often rudimentary even in mature as2 leaves. However, several parallel veins of very similar thickness were evident in such leaves. The malformed veins were visible prior to the development of asymmetry of the Leaf Lamina, and were maintained in the mature as2 leaves. Culture in vitro on phytohormone-free medium of Leaf sections from the as2 mutants and from the asymmetric leavesl (as1) mutant, which has a phenotype similar to that of as2, revealed an elevated potential in both cases for regeneration of shoots from Leaf cells. Analysis by the reverse transcription-polymerase chain reaction showed that AS2 and AS1 negatively regulates the homeobox genes KNAT1, KNAT2 and KNAT6 in leaves. Taken together, our results suggest that AS2 and AS1 are involved in establishment of Leaf venation and the formation of symmetric Leaf Lamina, which might be related to repression of expression of the homeobox genes in leaves.

Yasunori Machida - One of the best experts on this subject based on the ideXlab platform.

  • Formation of a Symmetric Flat Leaf Lamina in Arabidopsis
    Morphogenesis and Pattern Formation in Biological Systems, 2003
    Co-Authors: Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Endang Semiarti, Hirokazu Tsukaya, Mitsuyasu Hasebe, Shoko Kojima, Yasunori Machida
    Abstract:

    The ASYMMETRIC LEAVESI (AS1) and ASYMMETRIC LEAVES2 (AS2) genes of Arabidopsis thatiana are involved in the establishment of the Leaf venation system, which includes the prominent midvein, as well as in the development of a symmetric Lamina. The gene product also represses the expression of class 1 knox homeobox genes in leaves. We have characterized the AS2 gene, which appears to encode a novel protein with cysteine repeats (designated the C-motif), conserved glycine, and a leucine-zipper-like sequence in the amino-terminal half of the primary sequence. The Arabidopsis genome contains 42 putative genes that potentially encode proteins with conserved amino acid sequences in the amino-terminal half. Thus, the AS2 protein belongs to a novel family of proteins that we have designated the AS2 family. Members of this family except AS2 also have been designated ASLs (AS2-like proteins). Overexpression of AS2 cDNA in transgenic Arabidopsis plants resulted in upwardly curled leaves, which differed markedly from the downwardly curled leaves generated by loss-of-function mutation of AS2. Our results suggest that AS2 functions in the transcription of a certain gene(s) in plant nuclei and thereby controls the formation of a symmetric flat Leaf Lamina and the establishment of a prominent midvein and other patterns of venation.

  • the asymmetric leaves2 gene of arabidopsis thaliana regulates formation of a symmetric Lamina establishment of venation and repression of meristem related homeobox genes in leaves
    Development, 2001
    Co-Authors: Endang Semiarti, Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Hirokazu Tsukaya, Yasunori Machida
    Abstract:

    The asymmetric leaves2 (as2) mutant of Arabidopsis thaliana generated Leaf lobes and Leaflet-like structures from the petioles of leaves in a bilaterally asymmetric manner. Both the delayed formation of the primary vein and the asymmetric formation of secondary veins were apparent in Leaf primordia of as2 plants. A distinct midvein, which is the thickest vein and is located in the longitudinal center of the Leaf Lamina of wild-type plants, was often rudimentary even in mature as2 leaves. However, several parallel veins of very similar thickness were evident in such leaves. The complexity of venation patterns in all Leaf-like organs of as2 plants was reduced. The malformed veins were visible before the development of asymmetry of the Leaf Lamina and were maintained in mature as2 leaves. In vitro culture on phytohormone-free medium of Leaf sections from as2 mutants and from the asymmetric leaves1 (as1) mutant, which has a phenotype similar to that of as2, revealed an elevated potential in both cases for regeneration of shoots from Leaf cells. Analysis by the reverse transcription-polymerase chain reaction showed that transcripts of the KNAT1, KNAT2 and KNAT6 (a recently identified member of the class 1 knox family) genes accumulated in the leaves of both as2 and as1 plants but not of wild type. Transcripts of the STM gene also accumulated in as1 leaves. These findings suggest that, in leaves, the AS2 and AS1 genes repress the expression of these homeobox genes, which are thought to maintain the indeterminate cell state in the shoot apical meristem. Taken together, our results suggest that AS2 and AS1 might be involved in establishment of a prominent midvein and of networks of other veins as well as in the formation of the symmetric Leaf Lamina, which might be related to repression of class 1 knox homeobox genes in leaves.

  • The Asymmetric Leaves2 (AS2) Gene of Arabidopsis Thaliana Regulates Lamina Formation and is Required for Patterning of Leaf Venation
    Progress in Biotechnology, 2001
    Co-Authors: Endang Semiarti, Chiyoko Machida, Hidekazu Iwakawa, Yoshihisa Ueno, Hirokazu Tsukaya, Yasunori Machida
    Abstract:

    ABSTRACT To understand the molecular mechanisms behind symmetrical development of Leaf, we have analyzed the asymmetric leaves2 (as2) mutant of A. thaliana, which generated Leaf lobes and Leaflet-like structures from the petioles of leaves in a bilaterally asymmetric manner. The delayed formation of the primary vein and the asymmetric formation of secondary veins were apparent in Leaf primordia of as2 plants. A distinct midvein, which is the thickest vein and is located in the longitudinal center of the Leaf Lamina of wild-type plants, was often rudimentary even in mature as2 leaves. However, several parallel veins of very similar thickness were evident in such leaves. The malformed veins were visible prior to the development of asymmetry of the Leaf Lamina, and were maintained in the mature as2 leaves. Culture in vitro on phytohormone-free medium of Leaf sections from the as2 mutants and from the asymmetric leavesl (as1) mutant, which has a phenotype similar to that of as2, revealed an elevated potential in both cases for regeneration of shoots from Leaf cells. Analysis by the reverse transcription-polymerase chain reaction showed that AS2 and AS1 negatively regulates the homeobox genes KNAT1, KNAT2 and KNAT6 in leaves. Taken together, our results suggest that AS2 and AS1 are involved in establishment of Leaf venation and the formation of symmetric Leaf Lamina, which might be related to repression of expression of the homeobox genes in leaves.