The Experts below are selected from a list of 12861 Experts worldwide ranked by ideXlab platform
Hirokazu Tsukaya - One of the best experts on this subject based on the ideXlab platform.
-
morphogenesis of flattened unifacial leaves in juncus prismatocarpus juncaceae
New Phytologist, 2019Co-Authors: Hirokazu TsukayaAbstract:: To reveal the mode of morphogenesis of flattened unifacial leaves, we analysed the cell division direction and distribution on the Leaf Blade of Juncus prismatocarpus. Using the pulse-chase 5-ethynyl-2'-deoxyuridine method, we quantified and mapped the cell division direction on the Leaf Blade of J. prismatocarpus and compared the distribution of thickening cell divisions with the expression pattern of DROOPING Leaf (DL), a key gene involved in Leaf Blade thickening. Thickening cell divisions were the most abundant (> 45%) among all cell division directions on the Leaf Blade of J. prismatocarpus from the early plastochron 2 stage through the plastochron 3 stage. Mapping of cell divisions indicated that cell divisions in a particular direction were not restricted to a particular domain but were distributed diffusely throughout the entire cross-sectional area of the Leaf Blade. Gradient analysis indicated that the distribution of thickening cell divisions of the adaxial domain was denser than that of the abaxial domain. Contrary to the prolonged and diffuse distribution of thickening cell divisions, DL expression was transient and restricted in a narrow band. Our results suggest that a diffuse 'thickening meristem' plays the key role in the development of flattened unifacial leaves.
-
key proliferative activity in the junction between the Leaf Blade and Leaf petiole of arabidopsis
Plant Physiology, 2011Co-Authors: Yasunori Ichihashi, Gorou Horiguchi, Hirokazu Tsukaya, Kensuke Kawade, Takeshi Usami, Taku TakahashiAbstract:Leaves are the most important, fundamental units of organogenesis in plants. Although the basic form of a Leaf is clearly divided into the Leaf Blade and Leaf petiole, no study has yet revealed how these are differentiated from a Leaf primordium. We analyzed the spatiotemporal pattern of mitotic activity in Leaf primordia of Arabidopsis (Arabidopsis thaliana) in detail using molecular markers in combination with clonal analysis. We found that the proliferative zone is established after a short interval following the occurrence of a rod-shaped early Leaf primordium; it is separated spatially from the shoot apical meristem and seen at the junction region between the Leaf Blade and Leaf petiole and produces both Leaf-Blade and Leaf-petiole cells. This proliferative region in Leaf primordia is marked by activity of the ANGUSTIFOLIA3 (AN3) promoter as a whole and seems to be differentiated into several spatial compartments: activities of the CYCLIN D4;2 promoter and SPATULA enhancer mark parts of it specifically. Detailed analyses of the an3 and Blade-on-petiole mutations further support the idea that organogenesis of the Leaf Blade and Leaf petiole is critically dependent on the correct spatial regulation of the proliferative region of Leaf primordia. Thus, the proliferative zone of Leaf primordia is spatially differentiated and supplies both the Leaf-Blade and Leaf-petiole cells.
-
genetic framework for flattened Leaf Blade formation in unifacial leaves of juncus prismatocarpus
The Plant Cell, 2010Co-Authors: Takahiro Yamaguchi, Hirokazu Tsukaya, Satoshi YanoAbstract:Angiosperm leaves generally develop as bifacial structures with distinct adaxial and abaxial identities. However, several monocot species, such as iris and leek, develop unifacial leaves, in which Leaf Blades have only abaxial identity. In bifacial leaves, adaxial-abaxial polarity is required for Leaf Blade flattening, whereas many unifacial leaves become flattened despite their Leaf Blades being abaxialized. Here, we investigate the mechanisms underlying the development and evolution of flattened Leaf Blades in unifacial leaves. We demonstrate that the unifacial Leaf Blade is abaxialized at the gene expression level and that an ortholog of the DROOPING Leaf (DL) gene may promote flattening of the unifacial Leaf Blade. In two closely related Juncus species, Juncus prismatocarpus, which has flattened unifacial leaves, and Juncus wallichianus, which has cylindrical unifacial leaves, DL expression levels and patterns correlate with the degree of laminar outgrowth. Genetic and expression studies using interspecific hybrids of the two species reveal that the DL locus from J. prismatocarpus flattens the unifacial Leaf Blade and expresses higher amounts of DL transcript than does that from J. wallichianus. We also show that Leaf Blade flattening is a trigger for central-marginal Leaf polarity differentiation. We suggest that flattened unifacial Leaf Blades may have evolved via the recruitment of DL function, which plays a similar cellular but distinct phenotypic role in monocot bifacial leaves.
-
the different growth responses of the arabidopsis thaliana Leaf Blade and the petiole during shade avoidance are regulated by photoreceptors and sugar
Plant and Cell Physiology, 2005Co-Authors: Toshiaki Kozuka, Gorou Horiguchi, Hirokazu Tsukaya, Gyungtae Kim, Maki Ohgishi, Tatsuya SakaiAbstract:During the shade-avoidance response, Leaf Blade expansion is inhibited and petiole elongation is enhanced. In this study, we examined the roles of photoreceptors and sugar on the differential growth of the Leaf Blade and petiole in shade conditions. Under the conditions examined, cell expansion, not cell division, played a major role in the differential Leaf growth. The enhanced cell expansion in the Leaf Blade is associated with an increase in the ploidy level, whereas cell elongation was stimulated in the petiole in dark conditions without an increase in the ploidy level. Analysis of phytochrome, cryptochrome and phototropin mutants revealed that phytochromes and cryptochromes specifically regulate the contrasting growth patterns of the Leaf Blade and petiole in shade. Examination of the effects of photo-assimilated sucrose on the growth of the Leaf Blade and petiole revealed growth-promotional effects of sucrose that are highly dependent on the light conditions. The Leaf Blades of abscisic acid-deficient and sugar-insensitive mutants did not expand in blue light, but expanded normally in red light. These results suggest that both the regulation of light signals and the modulation of responses to sugar are important in the control of the differential photomorphogenesis of the Leaf Blade and petiole.
Million Tadege - One of the best experts on this subject based on the ideXlab platform.
-
control of Leaf Blade outgrowth and floral organ development by leunig angustifolia3 and wox transcriptional regulators
New Phytologist, 2019Co-Authors: Fei Zhang, Tezera W Wolabu, Hui Wang, Shweta Kalve, Jin Nakashima, John F Golz, Million TadegeAbstract:Plant lateral organ development is a complex process involving both transcriptional activation and repression mechanisms. The WOX transcriptional repressor WOX1/STF, the LEUNIG (LUG) transcriptional corepressor and the ANGUSTIFOLIA3 (AN3) transcriptional coactivator play important roles in Leaf Blade outgrowth and flower development, but how these factors coordinate their activities remains unclear. Here we report physical and genetic interactions among these key regulators of Leaf and flower development. We developed a novel in planta transcriptional activation/repression assay and suggest that LUG could function as a transcriptional coactivator during Leaf Blade development. MtLUG physically interacts with MtAN3, and this interaction appears to be required for Leaf and flower development. A single amino acid substitution at position 61 in the SNH domain of MtAN3 protein abolishes its interaction with MtLUG, and its transactivation activity and biological function. Mutations in lug and an3 enhanced each other's mutant phenotypes. Both the lug and the an3 mutations enhanced the wox1 prs Leaf and flower phenotypes in Arabidopsis. Our findings together suggest that transcriptional repression and activation mediated by the WOX, LUG and AN3 regulators function in concert to promote Leaf and flower development, providing novel mechanistic insights into the complex regulation of plant lateral organ development.
-
STENOFOLIA Recruits TOPLESS to Repress ASYMMETRIC LEAVES2 at the Leaf Margin and Promote Leaf Blade Outgrowth in Medicago truncatula
The Plant Cell, 2014Co-Authors: Fan Zhang, E. M. Kramer, Yongxing Wang, Y. Tang, Million TadegeAbstract:The Medicago truncatula WUSCHEL-related homeobox (WOX) gene, STENOFOLIA (STF), plays a key role in Leaf Blade outgrowth by promoting cell proliferation at the adaxial-abaxial junction. STF functions primarily as a transcriptional repressor, but the underlying molecular mechanism is unknown. Here, we report the identification of a protein interaction partner and a direct target, shedding light on the mechanism of STF function. Two highly conserved motifs in the C-terminal domain of STF, the WUSCHEL (WUS) box and the STF box, cooperatively recruit TOPLESS (Mt-TPL) family corepressors, and this recruitment is required for STF function, as deletion of these two domains (STFdel) impaired Blade outgrowth whereas fusing Mt-TPL to STFdel restored function. The homeodomain motif is required for direct repression of ASYMMETRIC LEAVES2 (Mt-AS2), silencing of which partially rescues the stf mutant phenotype. STF and LAMINALESS1 (LAM1) are functional orthologs. A single amino acid (Asn to Ile) substitution in the homeodomain abolished the repression of Mt-AS2 and STF's ability to complement the lam1 mutant of Nicotiana sylvestris. Our data together support a model in which STF recruits corepressors to transcriptionally repress its targets during Leaf Blade morphogenesis. We propose that recruitment of TPL/TPL-related proteins may be a common mechanism in the repressive function of modern/WUS clade WOX genes.
-
stenofolia acts as a repressor in regulating Leaf Blade outgrowth
Plant Signaling & Behavior, 2013Co-Authors: Hao Lin, Lifang Niu, Million TadegeAbstract:We recently reported that the Medicago WOX gene, STENOFOLIA (STF), acts as a transcriptional repressor in regulating Leaf Blade outgrowth. By using the Nicotiana sylvestris Bladeless lam1 mutant as a genetic tool, we showed that the WUS-box, which is conserved among WUS clade WOX genes, is partly responsible for the repressive activity of STF. All members of the modern/WUS clade genes (WUS, WOX1-WOX7) in Arabidopsis that contain intact WUS-box can substitute for STF/LAM1 function while the intermediate and ancient clade members including WOX9,WOX11 and WOX13 cannot, due to lack of the intact WUS-box. Taken together, our results reveal a conserved repression mechanism playing a central role in cell proliferation conferred to the evolutionarily dynamic WOX gene family with acquisition of a repressor domain.
-
evolutionarily conserved repressive activity of wox proteins mediates Leaf Blade outgrowth and floral organ development in plants
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Hao Lin, Neil A. Mchale, Lifang Niu, Masaru Ohmetakagi, Kirankumar S Mysore, Million TadegeAbstract:The WUSCHEL related homeobox (WOX) genes play key roles in stem cell maintenance, embryonic patterning, and lateral organ development. WOX genes have been categorized into three clades—ancient, intermediate, and modern/WUS—based on phylogenetic analysis, but a functional basis for this classification has not been established. Using the classical Bladeless lam1 mutant of Nicotiana sylvestris as a genetic tool, we examined the function of the Medicago truncatula WOX gene, STENOFOLIA (STF), in controlling Leaf Blade outgrowth. STF and LAM1 are functional orthologs. We found that the introduction of mutations into the WUS-box of STF (STFm1) reduces its ability to complement the lam1 mutant. Fusion of an exogenous repressor domain to STFm1 restores complementation, whereas fusion of an exogenous activator domain to STFm1 enhances the narrow Leaf phenotype. These results indicate that transcriptional repressor activity mediated by the WUS-box of STF acts to promote Blade outgrowth. With the exception of WOX7, the WUS-box is conserved in the modern clade WOX genes, but is not found in members of the intermediate or ancient clades. Consistent with this, all members of the modern clade except WOX7 can complement the lam1 mutant when expressed using the STF promoter, but members of the intermediate and ancient clades cannot. Furthermore, we found that fusion of either the WUS-box or an exogenous repressor domain to WOX7 or to members of intermediate and ancient WOX clades results in a gain-of-function ability to complement lam1 Blade outgrowth. These results suggest that modern clade WOX genes have evolved for repressor activity through acquisition of the WUS-box.
Kunihiko Ojima - One of the best experts on this subject based on the ideXlab platform.
-
tissue distribution of glutamate synthase and glutamine synthetase in rice leaves occurrence of nadh dependent glutamate synthase protein and activity in the unexpanded nongreen Leaf Blades
Plant Physiology, 1992Co-Authors: Tomoyuki Yamaya, Kazunari Kamachi, Toshihiko Hayakawa, Keisuke Tanasawa, Tadahiko Mae, Kunihiko OjimaAbstract:To further explore the function of NADH-dependent glutamate synthase (GOGAT), the tissue distribution of NADH-GOGAT protein and activity was investigated in rice (Oryza sativa L.) leaves. The distributions of ferredoxin (Fd)-dependent GOGAT, plastidic glutamine synthetase, and cytosolic glutamine synthetase proteins were also determined in the same tissues. High levels of NADH-GOGAT protein (33.1 μg protein/g fresh weight) and activity were detected in the 10th Leaf Blade before emergence. The unexpanded, nongreen portion of the 9th Leaf Blade contained more than 50% of the NADH-GOGAT protein and activity per gram fresh weight when compared with the 10th Leaf. The expanding, green portion of the 9th Leaf Blade outside of the sheath contained a slightly lower abundance of NADH-GOGAT protein than the nongreen portion of the 9th Blade on a fresh weight basis. The fully expanded Leaf Blades at positions lower than the 9th Leaf had decreased NADH-GOGAT levels as a function of increasing age, and the oldest, 5th Blade contained only 4% of the NADH-GOGAT protein compared with the youngest 10th Leaf Blade. Fd-GOGAT protein, on the other hand, was the major form of GOGAT in the green tissues, and the highest amount of Fd-GOGAT protein (111 μg protein/g fresh weight) was detected in the 7th Leaf Blade. In the nongreen 10th Leaf Blade, the content of Fd-GOGAT protein was approximately 7% of that found in the 7th Leaf Blade. In addition, the content of NADH-GOGAT protein in the 10th Leaf Blade was about 4 times higher than that of Fd-GOGAT protein. The content of plastidic glutamine synthetase polypeptide was also the highest in the 7th Leaf Blade (429 μg/g fresh weight) and lowest in nongreen Blades and sheaths. On the other hand, the relative abundance of the cytosolic glutamine synthetase polypeptide was the highest in the oldest Leaf Blade, decreasing to 10 to 20% of that value in young, nongreen leaves. These results suggest that NADH-GOGAT is important for the synthesis of glutamate from the glutamine that is transported from senescing source tissues through the phloem in the nongreen sink tissues in rice leaves.
-
Changes in Cytosolic Glutamine Synthetase Polypeptide and its mRNA in a Leaf Blade of Rice Plants during Natural Senescence.
Plant Physiology, 1992Co-Authors: Kazunari Kamachi, Tomoyuki Yamaya, Toshihiko Hayakawa, Kunihiko OjimaAbstract:Changes in the levels of cytosolic glutamine synthetase (GS1) and chloroplastic glutamine synthetase (GS2) polypeptides and of their corresponding mRNAs have been investigated in segments of the 13th Leaf of hydroponically grown rice (Oryza sativa L.) plants during natural senescence. The Leaf Blade on the main stem at early (0 day), middle (15 days), and late (25 days) stages of senescence was harvested and cut into 18 or 19 segments, 2 centimeters in length from the base to the tip. The amount of GS1 polypeptide, detected with specific antibody for the GS1, was greatest near the middle of the Leaf Blade (segments 11-13). There was little difference in the GS1 content between corresponding Leaf segments obtained at the early and middle stages of senescence. At the late senescence stage, all segments had lost some GS1 polypeptide, but more than 50% of GS1 detected at both the early and middle stages was still detectable in segments. The relative content of mRNA for GS1 in the total RNA in all segments was very low during early senescence but increased in all Leaf segments during later senescence. At the late stage of senescence, GS1 mRNA in the total RNA increased about 4.2- to 4.6-fold in segments 12 to 16 in the day-25 samples compared with those in the early stage. The content of the GS2 polypeptide, as well as ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) protein, was highest in segment 17 in the 0-day samples. During senescence, this peak became lower and broader, and finally disappeared, i.e. approximately 80% of GS2 polypeptide and Rubisco protein in segment 17 were lost by day 25. In contrast with GS2 polypeptide, the relative level of GS2 mRNA increased 1.8- to 2.9-fold in individual segments at the middle stage of senescence. Even at the late stage, the transcript signals remained slightly higher than those at the early stage in all segments. Thus, GS1 and GS2 polypeptides and corresponding mRNAs responded in a different manner within an attached rice Leaf during natural senescence. The contents of GS1 and GS2 polypeptides were not simply determined by the abundance of their corresponding mRNAs in the rice Leaf Blades during natural senescence.
Saman Seneweera - One of the best experts on this subject based on the ideXlab platform.
-
new insight into photosynthetic acclimation to elevated co2 the role of Leaf nitrogen and ribulose 1 5 bisphosphate carboxylase oxygenase content in rice leaves
Environmental and Experimental Botany, 2011Co-Authors: Saman Seneweera, Amane Makino, Naoki Hirotsu, Robert Norton, Yuji SuzukiAbstract:We tested the hypothesis that photosynthetic (A) acclimation to elevated CO2 partial pressure (p[CO2]) is associated with the inhibition of protein synthesis, inhibition of nitrogen (N) partitioning into the Leaf Blade and/or accelerated Leaf senescence in rice (Oryza sativa L. cv. Notohikari). Plants were grown for 70 days hydroponically in artificially illuminated growth chambers at a p[CO2] of either 39 or 100Pa at N 2mM. Leaf A, Vc.max, Jmax, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, E.C.4.1.1.39), mRNA for associated genes rbcS and rbcL, total N and carbohydrate concentrations in leaves at different positions in the canopy were measured. Spatial allocation of N and Rubisco synthesis of expanding Leaf Blade was also measured from the Leaf ligule to tip of the Leaf Blade. Growth at elevated p[CO2] suppressed light saturated A, Vc.max and Jmax in Leaf Blades at all positions in the canopy. The suppression of A was 15% for the upper Leaf Blades compared to 37% in the lower Leaf Blades. Similar reductions in the amount of Rubisco, Chlorophyll, and total N were observed in the leaves of the plants grown in 100 p[CO2] compared to the 39 p[CO2]. Sucrose and starch concentration concentrations increased at elevated p[CO2] but we found no relationship between A, Rubisco or the amount of transcript abundance of rbcS and rbcL. Elevated p[CO2] substantially reduced N allocation into expanding Leaf Blades and this was well correlated with Rubisco synthesis. These results suggest that A acclimation to elevated p[CO2] occurs during all phases of the Leaf development, is initiated during the cell maturation process and linked with spatial N allocation into the Leaf Blade. In addition, elevated p[CO2] accelerated lower Leaf Blade senescence which compounded the effect on A acclimation.
-
enhanced Leaf elongation rates of wheat at elevated co2 is it related to carbon and nitrogen dynamics within the growing Leaf Blade
Environmental and Experimental Botany, 2005Co-Authors: Saman Seneweera, Jann P ConroyAbstract:Abstract This paper addresses the question of whether Leaf elongation rates (LER) of monocots is controlled at high atmospheric CO2 by nitrogen (N) and/or carbohydrate concentrations in the zones of cell division and expansion in the basal meristem of growing Leaf Blades. Wheat (Triticum aestivum L. cv. Hartog) was grown at high N supplies at either 360 or 700 μmol CO2 mol−1 in artificially illuminated growth chambers for 30 days prior to final harvest to determine growth parameters and chemical composition of Leaf Blades. We particularly focused on the spatial distribution of carbon (C), N and carbohydrate concentrations along the expanding Leaf Blade. Elevated CO2 accelerated LER of expanding Blade (sixth Leaf Blade) by 32% and this factor contributed to increase in total Leaf area (18%) and shoots mass (36%). N concentrations in the expanding and last fully expanded Leaf Blade (LFEL) were reduced by 18% and 33%, respectively, at elevated CO2 but soluble carbohydrate concentrations were significantly increased in the expanded leaves only. N concentrations were highest in the zones of cell division and expansion of the elongating Blade but were unaffected by high CO2 and reductions in N concentration only appeared in the cell maturing zone where division and expansion had ceased. The concentration of soluble carbohydrates was greater in the cell division and expansion than in maturation zones but was unaffected by high CO2. C concentration was also little affected by elevated CO2 in any zone of the Blade. We conclude that greater availability of soluble carbohydrates for export from the expanded to expanding Blades is the driving force for accelerated LER at elevated CO2. It is unlikely that N concentrations limited Leaf growth at high CO2 because its concentration was unaffected by CO2 in the zones of cell division and expansion that are most sensitive to N supply.
-
diurnal regulation of Leaf Blade elongation in rice by co2 is it related to sucrose phosphate synthase activity
Plant Physiology, 1995Co-Authors: Saman Seneweera, Amarjit S Basra, Edward W Barlow, Jann P ConroyAbstract:The relationship between Leaf Blade elongation rates (LER) and sucrose-phosphate synthase (SPS) activity was investigated at different times during ontogeny of rice (Oryza sativa L. cv Jarrah) grown in flooded soil at either 350 or 700 [mu]L CO2 L-1. High CO2 concentrations increased LER of expanding Blades and in vivo activity (Vlimiting) SPS activity of expanded Blades during the early vegetative stage (21 d after planting [DAP]), when tiller number was small and growing Blades were strong carbohydrate sinks. Despite a constant light environment, there was a distinct diurnal pattern in LER, Vlimiting SPS activity, and concentration of soluble sugars, with an increase in the early part of the light period and a decrease later in the light period. The strong correlation (r = 0.65) between LER and Vlimiting SPS activity over the diurnal cycle indicated that SPS activity played an important role in controlling Blade growth. The higher Vlimiting SPS activity at elevated CO2 at 21 DAP was caused by an increase in the activation state of the enzyme rather than an increase in Vmax. Fructose and glucose accumulated to a greater extent than sucrose at high CO2 and may have been utilized for synthesis of cell-wall components, contributing to higher specific Leaf weight. By the mid-tillering stage (42 DAP), CO2 enrichment enhanced Vlimiting and Vmax activities of source Blades. Nevertheless, LER was depressed by high CO2, probably because tillers were stronger carbohydrate sinks than growing Blades.
Yanbin Hong - One of the best experts on this subject based on the ideXlab platform.
-
single cell rna seq describes the transcriptome landscape and identifies critical transcription factors in the Leaf Blade of the allotetraploid peanut arachis hypogaea l
Plant Biotechnology Journal, 2021Co-Authors: Hao Liu, Liping Wang, Xuanqiang Liang, Haiyan Liu, Xiaoping Chen, Rajeev K Varshney, Yanbin HongAbstract:Single-cell RNA-seq (scRNA-seq) has been highlighted as a powerful tool for the description of human cell transcriptome, but the technology has not been broadly applied in plant cells. Herein, we describe the successful development of a robust protoplast cell isolation system in the peanut Leaf. A total of 6,815 single cells were divided into eight cell clusters based on reported marker genes by applying scRNA-seq. Further, a pseudo-time analysis was used to describe the developmental trajectory and interaction network of transcription factors (TFs) of distinct cell types during Leaf growth. The trajectory enabled re-investigation of the primordium-driven development processes of the mesophyll and epidermis. These results suggest that palisade cells likely differentiate into spongy cells, while the epidermal cells originated earlier than the primordium. Subsequently, the developed method integrated multiple technologies to efficiently validate the scRNA-seq result in a homogenous cell population. The expression levels of several TFs were strongly correlated with epidermal ontogeny in accordance with obtained scRNA-seq values. Additionally, peanut AHL23 (AT-HOOK MOTIF NUCLEAR LOCALIZED PROTEIN 23), which is localized in nucleus, promoted Leaf growth when ectopically expressed in Arabidopsis by modulating the phytohormone pathway. Together, our study displays that application of scRNA-seq can provide new hypotheses regarding cell differentiation in the Leaf Blade of Arachis hypogaea. We believe that this approach will enable significant advances in the functional study of Leaf Blade cells in the allotetraploid peanut and other plant species.