Identification of BBX proteins as rate-limiting cofactors of HY5

As a source of both energy and environmental information, monitoring of incoming light is crucial for plants to optimize growth throughout development1. Concordantly, the light signalling pathways in plants are highly integrated with numerous other regulatory pathways2,3. One of these signal integrators is the basic leucine zipper domain (bZIP) transcription factor LONG HYPOCOTYL 5 (HY5), which has a key role as a positive regulator of light signalling in plants4,5. Although HY5 is thought to act as a DNA-binding transcriptional regulator6,7, the lack of any apparent transactivation domain8 makes it unclear how HY5 is able to accomplish its many functions. Here we describe the identification of three B-box containing proteins (BBX20, BBX21 and BBX22) as essential partners for HY5-dependent modulation of hypocotyl elongation, anthocyanin accumulation and transcriptional regulation. The bbx20 bbx21 bbx22 (bbx202122) triple mutant mimics the phenotypes of hy5 in the light and its ability to suppress the cop1 mutant phenotype in darkness. Furthermore, 84% of genes that exhibit differential expression in bbx202122 are also regulated by HY5, and we provide evidence that HY5 requires the B-box proteins for transcriptional regulation. Finally, expression of a truncated dark-stable version of HY5 (HY5(ΔN77)) together with BBX21 mutated in its VP motif strongly promoted de-etiolation in dark-grown seedlings, demonstrating the functional interdependence of these factors. In sum, this work clarifies long-standing questions regarding HY5 action and provides an example of how a master regulator might gain both specificity and dynamicity through the obligate dependence of cofactors

<i>Arabidopsis</i> RUP2 represses UVR8-mediated flowering in noninductive photoperiods.

Plants have evolved complex photoreceptor-controlled mechanisms to sense and respond to seasonal changes in day length. This ability allows plants to optimally time the transition from vegetative growth to flowering. UV-B is an important part intrinsic to sunlight; however, whether and how it affects photoperiodic flowering has remained elusive. Here, we report that, in the presence of UV-B, genetic mutation of &lt;i&gt;REPRESSOR OF UV-B PHOTOMORPHOGENESIS 2&lt;/i&gt; ( &lt;i&gt;RUP2&lt;/i&gt; ) renders the facultative long day plant &lt;i&gt;Arabidopsis thaliana&lt;/i&gt; a day-neutral plant and that this phenotype is dependent on the UV RESISTANCE LOCUS 8 (UVR8) UV-B photoreceptor. We provide evidence that the floral repression activity of RUP2 involves direct interaction with CONSTANS, repression of this key activator of flowering, and suppression of &lt;i&gt;FLOWERING LOCUS T&lt;/i&gt; transcription. RUP2 therefore functions as an essential repressor of UVR8-mediated induction of flowering under noninductive short day conditions and thus provides a crucial mechanism of photoperiodic flowering control

Genome-Wide Identification of R2R3-MYB Genes and Expression Analyses During Abiotic Stress in

The R2R3-MYB is one of the largest families of transcription factors, which have been implicated in multiple biological processes. There is great diversity in the number of R2R3-MYB genes in different plants. However, there is no report on genome-wide characterization of this gene family in cotton. In the present study, a total of 205 putative R2R3-MYB genes were identified in cotton D genome (Gossypium raimondii), that are much larger than that found in other cash crops with fully sequenced genomes. These GrMYBs were classified into 13 groups with the R2R3-MYB genes from Arabidopsis and rice. The amino acid motifs and phylogenetic tree were predicted and analyzed. The sequences of GrMYBs were distributed across 13 chromosomes at various densities. The results showed that the expansion of the G. Raimondii R2R3-MYB family was mainly attributable to whole genome duplication and segmental duplication. Moreover, the expression pattern of 52 selected GrMYBs and 46 GaMYBs were tested in roots and leaves under different abiotic stress conditions. The results revealed that the MYB genes in cotton were differentially expressed under salt and drought stress treatment. Our results will be useful for determining the precise role of the MYB genes during stress responses with crop improvement

Etude de divers parametres physicochimiques sur l'absorption,la migration etle devenir des metaux lourds dans les plantes

CNRS RP 185 (1869) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

ChlP-Seq reveals that QsMYB1 directly targets genes involved in lignin and suberin biosynthesis pathways in cork oak (Quercus suber)

Research ArticleBackground: Gene activity is largely controlled by transcriptional regulation through the action of transcription factors and other regulators. QsMYB1 is a member of the R2R3-MYB transcription factor family related to secondary growth, and in particular, with the cork development process. In order to identify the putative gene targets of QsMYB1 across the cork oak genome we developed a ChIP-Seq strategy. Results: Results provide direct evidence that QsMY1B targets genes encoding for enzymes involved in the lignin and suberin pathways as well as gene encoding for ABCG transporters and LTPs implicated in the transport of monomeric suberin units across the cellular membrane. These results highlight the role of QsMYB1 as a regulator of lignin and suberin biosynthesis, transport and assembly. Conclusion: To our knowledge, this work constitutes the first ChIP-Seq experiment performed in cork oak, a non-model plant species with a long-life cycle, and these results will contribute to deepen the knowledge about the molecular mechanisms of cork formation and differentiationinfo:eu-repo/semantics/publishedVersio