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Kotaro T. Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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space time analysis of gravitropism in etiolated arabidopsis Hypocotyls using bioluminescence imaging of the iaa19 promoter fusion with a destabilized luciferase reporter
Journal of Plant Research, 2017Co-Authors: Kotaro T. Yamamoto, Masaaki K Watahiki, Jun Matsuzaki, Soichirou Satoh, Hisayo ShimizuAbstract:Imaging analysis was carried out during the gravitropic response of etiolated Arabidopsis Hypocotyls, using an IAA19 promoter fusion of destabilized luciferase as a probe. From the bright-field images we obtained the local deflection angle to the vertical, A, local curvature, C, and the partial derivative of C with respect to time, $$\partial C/\partial t$$ . These were determined every 19.9 µm along the curvilinear length of the Hypocotyl, at ~10 min intervals over a period of ~6 h after turning Hypocotyls through 90° to the horizontal. Similarly from the luminescence images we measured the luminescence intensity of the convex and concave flanks of the Hypocotyl as well as along the median of the Hypocotyl, to determine differential expression of auxin-inducible IAA19. Comparison of these parameters as a function of time and curvilinear length shows that the gravitropic response is composed of three successive elements: the first and second curving responses and a decurving response (autostraightening). The maximum of the first curving response occurs when A is 76° along the entire length of the Hypocotyl, suggesting that A is the sole determinant in this response; in contrast, the decurving response is a function of both A and C, as predicted by the newly-proposed graviproprioception model (Bastien et al., Proc Natl Acad Sci USA 110:755–760, 2013). Further, differential expression of IAA19, with higher expression in the convex flank, is observed at A = 44°, and follows the Sachs’ sine law. This also suggests that IAA19 is not involved in the first curving response. In summary, the gravitropic response of Arabidopsis Hypocotyls consists of multiple elements that are each determined by separate principles.
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inhibition of brassinosteroid biosynthesis by either a dwarf4 mutation or a brassinosteroid biosynthesis inhibitor rescues defects in tropic responses of Hypocotyls in the arabidopsis mutant nonphototropic Hypocotyl 4
Plant Physiology, 2006Co-Authors: Daisuke Nakamoto, Akimitsu Ikeura, Tadao Asami, Kotaro T. YamamotoAbstract:The nonphototropic Hypocotyl 4 (nph4)/auxin response factor 7 (arf7) mutant of Arabidopsis (Arabidopsis thaliana) is insensitive to auxin and has defects in Hypocotyl tropism, hook formation, differential leaf growth, and lateral root formation. To understand an auxin-signaling pathway through NPH4, we carried out screening of suppressor mutants of nph4-103 and obtained a dwarf suppressor mutant, suppressor of nph4 (snp2). snp2 had short Hypocotyls in the dark condition and dark green and round leaves, short petioles, and more lateral shoots than the wild type in the light condition. The snp2 phenotypes were rescued by adding brassinolide to the growth medium in both light and dark conditions. Genetic mapping, sequence analysis, and a complementation test indicated that snp2 was a weak allele of DWARF4 (DWF4), which functions in brassinosteroid (BR) biosynthesis. snp2, which was renamed dwf4-101, exhibited photo- and gravitropisms of Hypocotyls similar to those of the wild type with a slightly faster response in gravitropism. dwf4-101 almost completely suppressed defects in both tropisms of nph4-103 Hypocotyls and completely suppressed hyponastic growth of nph4-103 leaves. Treatment with brassinazole, an inhibitor of BR biosynthesis, also partially rescued the tropic defects in nph4-103. Hypocotyls of nph4-103 were auxin insensitive, whereas Hypocotyls of dwf4-101 were more sensitive than those of the wild type. dwf4-101 nph4-103 Hypocotyls were as sensitive as those of dwf4-101. Auxin inducibility of massugu 2 (MSG2)/IAA19 gene expression was reduced in nph4-103. mRNA level of MSG2 was reduced in dwf4-101 and dwf4-101 nph4-103, but both mutants exhibited greater auxin inducibility of MSG2 than the wild type. Taken together, dwf4-101 was epistatic to nph4-103. These results strongly suggest that BR deficiency suppresses nph4-103 defects in tropic responses of Hypocotyls and differential growth of leaves and that BR negatively regulates tropic responses.
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massugu2 encodes aux iaa19 an auxin regulated protein that functions together with the transcriptional activator nph4 arf7 to regulate differential growth responses of Hypocotyl and formation of lateral roots in arabidopsis thaliana
The Plant Cell, 2004Co-Authors: Kiyoshi Tatematsu, Masaaki K Watahiki, Satoshi Kumagai, Atsuko Sato, Renee M Harper, Hideki Muto, Emmanuel Liscum, Kotaro T. YamamotoAbstract:We have isolated a dominant, auxin-insensitive mutant of Arabidopsis thaliana, massugu2 (msg2), that displays neither Hypocotyl gravitropism nor phototropism, fails to maintain an apical hook as an etiolated seedling, and is defective in lateral root formation. Yet other aspects of growth and development of msg2 plants are almost normal. These characteristics of msg2 are similar to those of another auxin-insensitive mutant, non-phototropic Hypocotyl4 (nph4), which is a loss-of-function mutant of AUXIN RESPONSE FACTOR7 (ARF7) (Harper et al., 2000). Map-based cloning of the MSG2 locus reveals that all four mutant alleles result in amino acid substitutions in the conserved domain II of an Auxin/Indole-3-Acetic Acid protein, IAA19. Interestingly, auxin inducibility of MSG2/IAA19 gene expression is reduced by 65% in nph4/arf7. Moreover, MSG2/IAA19 protein binds to the C-terminal domain of NPH4/ARF7 in a Saccharomyces cerevisiae (yeast) two-hybrid assay and to the whole latter protein in vitro by pull-down assay. These results suggest that MSG2/IAA19 and NPH4/ARF7 may constitute a negative feedback loop to regulate differential growth responses of Hypocotyls and lateral root formation.
Jose De Leon - One of the best experts on this subject based on the ideXlab platform.
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nitric oxide responses in arabidopsis Hypocotyls are mediated by diverse phytohormone pathways
Journal of Experimental Botany, 2018Co-Authors: Maricruz Castillo, Alberto Coego, Alvaro Costabroseta, Jose De LeonAbstract:Plants are often exposed to high levels of nitric oxide (NO) that affects development and stress-triggered responses. However, the way in which plants sense NO is still largely unknown. Here we combine the analysis of early changes in the transcriptome of plants exposed to a short acute pulse of exogenous NO with the identification of transcription factors (TFs) involved in NO sensing. The NO-responsive transcriptome was enriched in hormone homeostasis- and signaling-related genes. To assess events involved in NO sensing in Hypocotyls, we used a functional sensing assay based on the NO-induced inhibition of Hypocotyl elongation in etiolated seedlings. Hormone-related mutants and the TRANSPLANTA collection of transgenic lines conditionally expressing Arabidopsis TFs were screened for NO-triggered Hypocotyl shortening. These approaches allowed the identification of hormone-related TFs, ethylene perception and signaling, strigolactone biosynthesis and signaling, and salicylate production and accumulation that are essential for or modulate Hypocotyl NO sensing. Moreover, NO inhibits Hypocotyl elongation through the positive and negative regulation of some abscisic acid (ABA) receptors and transcripts encoding brassinosteroid signaling components thereby also implicating these hormones in NO sensing.
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nitric oxide regulates della content and pif expression to promote photomorphogenesis in arabidopsis
Plant Physiology, 2011Co-Authors: Jorge Lozanojuste, Jose De LeonAbstract:The transition from etiolated to green seedlings involves a shift from Hypocotyl growth-promoting conditions to growth restraint. These changes occur through a complex light-driven process involving multiple and tightly coordinated hormonal signaling pathways. Nitric oxide (NO) has been lately characterized as a regulator of plant development interacting with hormone signaling. Here, we show that Arabidopsis (Arabidopsis thaliana) NO-deficient mutant Hypocotyls are longer than those from wild-type seedlings under red light but not under blue or far-red light. Accordingly, exogenous treatment with the NO donor sodium nitroprusside and mutant plants with increased endogenous NO levels resulted in reduced Hypocotyl length. In addition to increased Hypocotyl elongation, NO deficiency led to increased anthocyanin levels and reduced PHYB content under red light, all processes governed by phytochrome-interacting factors (PIFs). NO-deficient plants accordingly showed an enhanced expression of PIF3, PIF1, and PIF4. Moreover, exogenous NO increased the levels of the gibberellin (GA)-regulated DELLA proteins and shortened Hypocotyls, likely through the negative regulation of the GA Insensitive Dwarf1 (GID1)-Sleepy1 (SLY1) module. Consequently, NO-deficient seedlings displayed up-regulation of SLY1, defective DELLA accumulation, and altered GA sensitivity, thus resulting in defective deetiolation under red light. Accumulation of NO in wild-type seedlings undergoing red light-triggered deetiolation and elevated levels of NO in the GA-deficient ga1-3 mutant in darkness suggest a mutual NO-GA antagonism in controlling photomorphogenesis. PHYB-dependent NO production promotes photomorphogenesis by a GID1-GA-SLY1-mediated mechanism based on the coordinated repression of growth-promoting PIF genes and the increase in the content of DELLA proteins.
Paula M Pijut - One of the best experts on this subject based on the ideXlab platform.
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agrobacterium mediated transformation of fraxinus pennsylvanica Hypocotyls and plant regeneration
Plant Cell Reports, 2009Co-Authors: Ningxia Du, Paula M PijutAbstract:A genetic transformation protocol for green ash (Fraxinus pennsylvanica) Hypocotyl explants was developed. Green ash Hypocotyls were transformed using Agrobacterium tumefaciens strain EHA105 harboring binary vector pq35GR containing the neomycin phosphotransferase (nptII) and β-glucuronidase (GUS) fusion gene, and an enhanced green fluorescent protein gene. Pre-cultured Hypocotyl explants were transformed in the presence of 100 μM acetosyringone using 90 s sonication plus 10 min vacuum-infiltration. Kanamycin at 20 mg l−1 was used for selecting transformed cells. Adventitious shoots regenerated on Murashige and Skoog medium supplemented with 13.3 μM 6-benzylaminopurine, 4.5 μM thidiazuron, 50 mg l−1 adenine sulfate, and 10% coconut water. GUS- and polymerase chain reaction (PCR)-positive shoots from the cut ends of Hypocotyls were produced via an intermediate callus stage. Presence of the GUS and nptII genes in GUS-positive shoots were confirmed by PCR and copy number of the nptII gene in PCR-positive shoots was determined by Southern blotting. Three transgenic plantlets were acclimatized to the greenhouse. This transformation and regeneration system using Hypocotyls provides a foundation for Agrobacterium-mediated transformation of green ash. Studies are underway using a construct containing the Cry8Da protein of Bacillus thuringiensis for genetic transformation of green ash.
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regeneration of plants from fraxinus pennsylvanica Hypocotyls and cotyledons
Scientia Horticulturae, 2008Co-Authors: Ningxia Du, Paula M PijutAbstract:Abstract An adventitious shoot regeneration and rooting protocol was developed for green ash (Fraxinus pennsylvanica) seedling explants. The best regeneration medium for freshly isolated Hypocotyls and cotyledons was Murashige and Skoog (MS) supplemented with 13.3 μM 6-benzylaminopurine (BA) plus 4.5 μM thidiazuron (TDZ), and 22.2 μM BA plus 4.5 μM TDZ, respectively. Seventy-six percent of Hypocotyl segments and 24% of cotyledon segments produced adventitious shoots, with a mean number of adventitious shoots per explant of 2.7 ± 0.5 and 2.3 ± 1.3, respectively. The effect of in vitro-germinated seedling age on adventitious shoot regeneration from Hypocotyl and cotyledon explants was also studied. Results showed that Hypocotyl and cotyledon explants from freshly isolated embryos exhibited a higher organogenesis potential than 4–15-day-old explants. Adventitious shoots from Hypocotyls and cotyledons were established as proliferating shoot cultures following transfer to MS basal medium with Gamborg B5 vitamins supplemented with 10 μM BA plus 10 μM TDZ. A high rooting percentage (73–90%) was achieved when in vitro shoots were rooted on woody plant medium (WPM) containing 4.9 μM indole-3-butyric acid (IBA) and IAA (0, 2.9, 5.7, or 8.6 μM) with a combination of 10-day dark culture period followed by a 16-h photoperiod. The highest rooting (90%) of adventitious shoots or the number of roots per shoot (3.0 ± 1.0) was obtained on WPM with 4.9 μM IBA plus 5.7 μM IAA. Rooted plants were successfully acclimatized to the greenhouse and 100% survived after overwintering in cold storage. This regeneration system using Hypocotyls and cotyledons provides a foundation for Agrobacterium-mediated genetic transformation of F. pennsylvanica for resistance to the emerald ash borer.
V K Sawhney - One of the best experts on this subject based on the ideXlab platform.
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reduced de etiolation of Hypocotyl growth in a tomato mutant is associated with hypersensitivity to and high endogenous levels of abscisic acid
Journal of Experimental Botany, 2001Co-Authors: Martin Fellner, Ruichuan Zhang, Richard P Pharis, V K SawhneyAbstract:A recessive single gene mutant, 7B-1, in tomato was originally selected for its photoperiod-dependent male sterility. The 7B-1 mutant also has some pleiotropic effects including reduced light-induced inhibition, i.e. de-etiolation, of the Hypocotyl in long days (LD), increased seed size and weight, and reduced transpiration rate. These traits led us to investigate the sensitivity of 7B-1 to exogenous hormones and the interaction of these responses with daylength. In LD, but not in short days (SD), 7B-1 was more sensitive than wild-type (WT) to exogenous abscisic acid (ABA) for inhibition of seed germination, root elongation and transpiration rate. 7B-1 mutant also exhibited reduced responses to exogenous gibberellin (GA(3)) for Hypocotyl elongation, and to inhibitors of GA biosynthesis for seed germination and root and Hypocotyl elongation. 7B-1 Hypocotyls contained a higher level of endogenous ABA than WT in both photoperiods, although ABA levels were higher in LD than in SD. In contrast, growth-active GAs, i.e. GA(1), GA(3) and GA(4), and IAA were low in the mutant Hypocotyls. The 7B-1 mutant appears to be an ABA-overproducer, and the photoperiod-regulated ABA levels may be responsible for the hypersensitivity of the mutant to exogenous ABA.
Giltsu Choi - One of the best experts on this subject based on the ideXlab platform.
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EARLY STARVATION 1 Is a Functionally Conserved Protein Promoting Gravitropic Responses in Plants by Forming Starch Granules
'Frontiers Media SA', 2021Co-Authors: Kijong Song, Dae-woo Lee, Jeongheon Kim, Jaewook Kim, Hwanuk Guim, Keunhwa Kim, Jong-seong Jeon, Giltsu ChoiAbstract:Starch granules in the endodermis of plant Hypocotyls act as statoliths that promote Hypocotyl negative gravitropism—the directional growth of Hypocotyls against gravity—in the dark. To identify the molecular components that regulate Hypocotyl negative gravitropism, we performed a mutagenesis screen and isolated reduced gravitropic 1 (rgv1) mutants that lack starch granules in their Hypocotyl endodermis and show reduced Hypocotyl negative gravitropism in the dark. Using whole genome sequencing, we identified three different rgv1 mutants that are allelic to the previously reported early starvation 1 mutant, which is rapidly depleted of starch just before the dawn. ESV1 orthologs are present in starch-producing green organisms, suggesting ESV1 is a functionally conserved protein necessary for the formation of starch granules. Consistent with this, we found that liverwort and rice ESV1 can complement the Arabidopsis ESV1 mutant phenotype for both starch granules and Hypocotyl negative gravitropism. To further investigate the function of ESV1 in other plants, we isolated rice ESV1 mutants and found that they show reduced levels of starch in their leaves and loosely packed starch granules in their grains. Both Arabidopsis and rice ESV1 mutants also lack starch granules in root columella and show reduced root gravitropism. Together, these results indicate ESV1 is a functionally conserved protein that promotes gravitropic responses in plants via its role in starch granule formation
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epidermal phytochrome b inhibits Hypocotyl negative gravitropism non cell autonomously
The Plant Cell, 2016Co-Authors: Kijong Song, Eunae Park, Giltsu ChoiAbstract:Seedling Hypocotyls display negative gravitropism in the dark but agravitropism in the light. The Arabidopsis thaliana pif quadruple mutant (pifQ), which lacks four PHYTOCHROME-INTERACTING FACTORS (PIFs), is agravitropic in the dark. Endodermis-specific expression of PIF1 rescues gravitropism in pifQ mutant seedlings. Since phytochromes induce light responses by inhibiting PIFs and the COP1-SPA ubiquitin E3 ligase complex in the nucleus, we asked whether phyB can cell autonomously inhibit Hypocotyl negative gravitropism in the endodermis. We found that while epidermis-specific expression of PHYB rescues Hypocotyl negative gravitropism and all other phyB mutant phenotypes, endodermis-specific expression of PHYB does not. Epidermal phyB induces the phosphorylation and degradation of endodermal PIFs in response to red light. This induces a global gene expression pattern similar to that induced by red light treatment of seedlings expressing PHYB under the control of its own endogenous promoter. Our results imply that epidermal phyB generates an unidentified mobile signal that travels to the endodermis where it promotes PIF degradation and inhibits Hypocotyl negative gravitropism.
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phytochromes promote seedling light responses by inhibiting four negatively acting phytochrome interacting factors
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Jieun Shin, Ismayil S Zulfugarov, Hyojin Kang, Giltsu ChoiAbstract:PIF3 is a phytochrome-interacting basic helix–loop–helix transcription factor that negatively regulates light responses, including Hypocotyl elongation, cotyledon opening, and Hypocotyl negative gravitropism. However, the role of PIF3 in chlorophyll biosynthesis has not been clearly defined. Here, we show that PIF3 also negatively regulates chlorophyll biosynthesis by repressing biosynthetic genes in the dark. Consistent with the gene expression patterns, the etiolated pif3 mutant accumulated a higher amount of protochlorophyllide and was bleached severely when transferred into light. The photobleaching phenotype of pif3 could be suppressed by the gun5 mutation and mimicked by overexpression of GUN5. When 4 negative phytochrome-interacting protein genes (PIF1, PIF3, PIF4, and PIF5) were mutated, the resulting quadruple mutant seedlings displayed constitutive photomorphogenic phenotypes, including short Hypocotyls, open cotyledons, and disrupted Hypocotyl gravitropism in the dark. Microarray analysis further confirmed that the dark-grown quadruple mutant has a gene expression pattern similar to that of red light-grown WT. Together, our data indicate that 4 phytochrome-interacting proteins are required for skotomorphogenesis and phytochromes activate photomorphogenesis by inhibiting these factors.