Project description: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.
Project description:The quintuple jaz mutant jazQ and the phytochrome mutant phyB-9 affect plant growth and defense. We used RNA-sequencing to query the transcriptomes of jazQ and phyB-9, as well as the combined jazQ phyB-9 sextuple mutatant, and examined how these mutations alter the expression of growth- and defense-associated genes. The data highlight how jasmonate and light signaling pathways contribute to growth and defense, and how their removal genetically promotes additive responses.
Project description:Phytochrome B (phyB), one member of phytochrome family in rice, plays important roles in regulating a range of developmental processes, and stress responses. However, little information about the mechanism involved in phyB-mediated light signaling pathway has been reported in rice. Another, it has been well-known that microRNAs (miRNAs) perform important roles in plant development and stress responses. Thus it is intriguing to explore the role of miRNAs in phyB-mediated light signaling pathway in rice. In this study, comparative high-throughput sequencing and degradome analysis were adopted to identify candidate miRNAs and their targets that participate in phyB-mediated light signaling pathway. A total of 838 known miRNAs, 663 novel miRNAs and 1,957 target genes were identified from wild-type (WT) and phyB mutant. Among them, 135 miRNAs showed differential expression, suggesting that the expressions of these miRNAs are under the control of phyB. In addition, 32 out of the 135 differentially expressed miRNAs were detected to slice 70 genes in rice genome. Analysis of these target genes showed that members of various transcription factor families constitute the largest proportion, indicating miRNAs are probably involved in phyB-mediated light signaling pathway mainly via regulating the expression of transcription factors. This study presented a comprehensive expression analysis of miRNAs and their targets that might be involved in phyB-mediated light signaling pathway for the first time. The results provide new clues for functional characterization of miRNAs in phyB-mediated light signaling pathway, which would be helpful in comprehensively uncovering molecular mechanism of phytochrome-mediated photomorphogenesis and stress responses in plant. Examination of miRNA profiles in wild type (WT) and phyB mutant at four-leaf stage by deep sequencing using Illumina Hiseq2500.
Project description:Phytochromes are evolutionarily conserved photoreceptors in bacteria, fungi, and plants. The prototypical phytochrome comprises an N-terminal photosensory module and a C-terminal histidine kinase signaling-output module. However, the plant phytochrome has been postulated to transduce light signals by interacting with a group of nodal Phytochrome-Interacting transcription Factors (PIFs) and triggering their degradation via the N-terminal photosensory module, while its C-terminal output module, including a Histidine Kinase-Related Domain (HKRD), is thought not to participate directly in signaling. Here, we show that the C-terminal module of Arabidopsis phytochrome B (PHYB) is unexpectedly sufficient to mediate the degradation of PIF3 and to induce a distinct set of PIF-regulated photosynthetic genes. These signaling functions require the HKRD and particularly its dimerization. A D1040V mutation, which disrupts the dimerization of HKRD and the interaction between the C-terminal module and PIF3, abrogates the early light signaling functions of PHYB in nuclear accumulation, photobody biogenesis, and PIF3 degradation. In contrast, disruption of the interaction between PIF3 and PHYB’s N-terminal photosensory module has little effect on PIF3 degradation. Together, this study provides novel insight into the central mechanism of early phytochrome signaling that the C-terminal signaling-output module of PHYB interacts with PIF3 in the nucleus to mediate PIF3 degradation by light.
Project description:The phytochrome family consists of five numbers (phyA-phyE) in Arabidopsis, of which phyB is the best characterized and shown to play a major role in mediating red light inhibition of hypocotyl elongation. In order to reveal the molecular basis for phyB-mediated red light signaling to promote photomorphogenesis, we analyzed the gene expression profile of red light-grown WT and phyB mutant seedlings by high throughput sequencing.
Project description:In this study we used genetic approaches and transcriptome profiling to unravel the complex interaction of different developmental pathways required for chloroplast development in plants. The recently described snowy cotyledon 3 (sco3) mutant as well as the Phytochrome B (phyb) mutant revealed, in the double mutant, a complex suppressive or additive genetically linked regulation of chloroplast development, flowering time and transcription regulation. Transcriptional profilling of mutants with aberrant chloroplast development: sco3, phyb and the double mutant sco3phyb.
Project description:To identify and characterize genes required for tissue-specific phytochrome responses during hypocotyl development in far-red-light grown bvr lines, we performed gene transcriptional profiling using bvr lines with mesophyll-specific phytochrome inactivation (cab3: :pBVR2). We identified several candidate genes whose expression is significantly altered in lines with mesophyll tissue-specific BVR expression (Cab3::pBVR2), compared to constitutive phytochrome inactivation lines, i.e. 35S-driven BVR lines (35S::pBVR3). No-0 is used as wild-type (WT)
Project description:Phytochrome B (phyB), one member of phytochrome family in rice, plays important roles in regulating a range of developmental processes, and stress responses. However, little information about the mechanism involved in phyB-mediated light signaling pathway has been reported in rice. Another, it has been well-known that microRNAs (miRNAs) perform important roles in plant development and stress responses. Thus it is intriguing to explore the role of miRNAs in phyB-mediated light signaling pathway in rice. In this study, comparative high-throughput sequencing and degradome analysis were adopted to identify candidate miRNAs and their targets that participate in phyB-mediated light signaling pathway. A total of 838 known miRNAs, 663 novel miRNAs and 1,957 target genes were identified from wild-type (WT) and phyB mutant. Among them, 135 miRNAs showed differential expression, suggesting that the expressions of these miRNAs are under the control of phyB. In addition, 32 out of the 135 differentially expressed miRNAs were detected to slice 70 genes in rice genome. Analysis of these target genes showed that members of various transcription factor families constitute the largest proportion, indicating miRNAs are probably involved in phyB-mediated light signaling pathway mainly via regulating the expression of transcription factors. This study presented a comprehensive expression analysis of miRNAs and their targets that might be involved in phyB-mediated light signaling pathway for the first time. The results provide new clues for functional characterization of miRNAs in phyB-mediated light signaling pathway, which would be helpful in comprehensively uncovering molecular mechanism of phytochrome-mediated photomorphogenesis and stress responses in plant.
Project description:Phytochromes mediate a profound developmental shift when dark-grown seedlings are exposed to light. Here we show that a subset of genes is up regulated in phytochrome B (phyB) mutants even before dark-grown seedlings are exposed to light. Most of these genes bear the RY cis motif, which is a binding site of the transcription factor ABSCISIC ACID INSENSITIVE 3 (ABI3), and the phyB mutation also enhanced ABI3 expression. These changes in transcriptome have physiological consequences as seedlings of the abi3 mutant showed enhanced responses to pulses of far-red light, while ABI3 overexpressers exhibited the opposite pattern. Seedlings of the wild type derived from seeds germinated in full darkness showed enhanced expression of genes bearing the RY cis motif and reduced responses to far-red light. We propose that, via changes in ABI3 expression, light, perceived mainly by phyB in the seed, generates a downstream trans-developmental phase signal that pre-conditions the seedling to its most likely environment. , ,
Project description:Plant photomorphogenesis and skotomorphogenesis depend on interplay of various plant hormones. Brassinosteroids (BRs) play crucial roles during hypocotyl establishment both in the light and darkness. Arabidopsis brassinosteroid insensitive1 (bri1-5) is a partial loss-of-function mutant, and the short-hypocotyl phenotype of bri1-5 is greatly suppressed by a long-hypocotyl mutant phytochrome B (pbyB-77) at the double mutant for the two in the light conditions to display additive phenotypes of both. To identify the genes responsible for this genetic interaction, we employed microarray analysis with the RNAs prepared from wild type, bri1-5, phyB-77, and bri1-5 phyB-77 double mutant. Microarray analysis supported the notion that PHYB acts upstream of BRs.