Biology subjects

Legris, M.

Publications and source records attributed to Legris, M..

5 recordsLinked to original sources

bioRxiv2022

PICLN modulates alternative splicing and ensures adaptation to light and temperature changes in plants

Plants undergo transcriptome reprogramming to adapt to daily and seasonal fluctuations in light and temperature conditions. While most efforts have focused on the role of master transcription factors, the importance of splicing factors modulating these processes is now emerging. Efficient pre-mRNA splicing depends on proper spliceosome assembly, which in plants and animals requires the methylosome complex. PICLN is part of the methylosome complex in both humans and Arabidopsis thaliana, and we show here that the human PICLN ortholog rescues phenotypes of A. thaliana picln mutants. Altered photomorphogenic and photoperiodic responses in A. thaliana picln mutants are associated with changes in pre-mRNA splicing, which partially overlap with those in prmt5 mutants. Mammalian PICLN also acts in concert with the Survival Motor Neuron (SMN) complex component GEMIN2 to modulate the late steps of UsnRNP assembly, and many alternative splicing events regulated by PICLN but not PROTEIN-ARGININE METHYL TRANSFERASE 5 (PRMT5), the main protein of the methylosome, are controlled by A. thaliana GEMIN2. As with GEMIN2 and SME1/PCP, low temperature, which increases PICLN expression, aggravates morphological and molecular defects of picln mutants. Taken together, these results establish a key role for PICLN in the regulation of pre-mRNA splicing and in mediating plant adaptation to daily and seasonal fluctuations in environmental conditions.

plant biology↗

bioRxiv2021

Day length-dependent thermal COP1 dynamics integrate conflicting seasonal cues in the control of Arabidopsis elongation

As the summer approaches, plants experience enhanced light inputs and elevated temperatures, two environmental cues with an opposite morphogenic impact. How plants integrate this conflicting information throughout seasons remains unclear. Key components of the plant response to light and temperature include phytochrome B (phyB), PHYTOCROME INTERACTING FACTOR 4 (PIF4), EARLY FLOWERING 3 (ELF3) and CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1). Here, we used hypocotyl lengths of single and double mutant/over-expression lines to fit a mathematical model incorporating known interactions of these genes. The fitted model recapitulates day length-dependent thermoelongation of all lines studied, and correctly predicts temperature responsiveness of new genotypes. Whilst previous works pointed to a lightindependent thermal function of COP1, simulations of our model suggested that COP1 has a role in temperature-signaling only during daytime. Based on by this prediction, we show that COP1 overexpression increases thermal response in continuous white light, while it has little effect in darkness. Defective thermal response of cop1-4 mutants is epistatic to phyB-9 and elf3-8, indicating that COP1 activity is essential to the transduction of phyB and ELF3 thermosensory function. Our model accurately captures phyB, ELF3 and PIF4 dynamics, providing an excellent toolbox for identification of best allelic combinations towards optimized crops resilience to climate change at different geographical latitudes.

plant biology↗

bioRxiv2021

Phototropin-mediated perception of light direction in Arabidopsis leaves regulates blade flattening

One conserved feature among angiosperms is the development of flat thin leaves. This developmental pattern optimizes light capture and gas exchange for photosynthesis. The blue light receptors phototropins are required for leaf flattening, with the null phot1phot2 mutant showing downwards curled leaves in Arabidopsis. However, key aspects of their function in leaf development remain unknown. Here, we performed a detailed spatiotemporal characterization of phototropin function in Arabidopsis leaves. We found that phototropins perceive light direction in the leaf blade, and similar to their role in hypocotyls they control the spatial pattern of auxin signaling possibly modulating auxin transport, to ultimately regulate cell expansion. Phototropin signaling components in the leaf partially differ from hypocotyls. Moreover, the light response on the upper (adaxial) and lower (abaxial) sides of the leaf blade suggest a partially distinct requirement of phototropin signaling components on each side. In particular, NON PHOTOTROPIC HYPOCOTYL 3 (NPH3) showed an adaxial-specific function. In addition, we show a prominent role of PHYTOCHROME KINASE SUBSTRATE 3 (PKS3) in leaf flattening. Among the auxin transporters tested, PINs and AUX/LAX influence the response most prominently. Overall, our results show that directional blue light perception by the phototropins is a key aspect of leaf development, integrating endogenous and exogenous signals. One sentence summaryPhototropins perceive light direction in the leaf and control the auxin signaling pattern to regulate blade flattening.

plant biology↗

bioRxiv2020

COP1 destabilizes DELLA proteins in Arabidopsis

DELLA transcriptional regulators are central components in the control of plant body form in response to the environment. This is considered to be mediated by changes in the metabolism of the hormones gibberellins (GAs), which promote the degradation of DELLAs. However, here we show that warm temperature or shade reduced the stability of a GA-insensitive DELLA allele in Arabidopsis. Furthermore, the degradation of DELLA induced by the warmth anticipated changes in GA levels and depended on the E3 ubiquitin ligase CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). COP1 enhanced the degradation of normal and GA-insensitive DELLA alleles when co-expressed in N. benthamiana. DELLA proteins physically interacted with COP1 in yeast, mammalian and plant cells. This interaction was enhanced by the COP1 complex partner SUPRESSOR OF phyA-105 1 (SPA1). The level of ubiquitination of DELLA was enhanced by COP1 and COP1 ubiquitinated DELLA proteins in vitro. We propose that DELLAs are destabilized not only by the canonical GA-dependent pathway but also by COP1 and that this control is relevant for growth responses to shade and warm temperature. SignificanceDELLA proteins are plant-specific transcriptional regulators that act as signaling hubs at the interface between the environment and the transcriptional networks that control growth. DELLAs are destabilized by the growth-promoting hormone gibberellin, whose levels are very sensitive to environmental changes. Here we describe an alternative pathway to destabilize these proteins. We show that DELLAs are substrate of COP1, an E3 ubiquitin ligase that increases its nuclear activity to promote growth in response to shade or warmth. Our results also show that the destabilization of DELLAs by COP1 precedes the action of gibberellins, suggesting the existence of a sequential mechanism to control the stability of these proteins.

plant biology↗

bioRxiv2018

Neighbor signals perceived by phytochrome B increase thermotolerance in Arabidopsis

Due to the preeminence of reductionist approaches, our understanding of plant responses to combined stresses is limited. We speculated that light-quality signals of neighboring vegetation might increase susceptibility to heat shocks because shade reduces tissue temperature and hence the likeness of heat shocks. In contrast, plants of Arabidopsis thaliana grown under low red / far-red ratios typical of shade were less damaged by heat stress than plants grown under simulated sunlight. Shade reduces the activity of phytochrome B (phyB) and the phyB mutant showed high tolerance to heat stress even under simulated sunlight. The enhanced heat tolerance under low red / far-red ratios failed in a multiple mutant of PHYTOCHROME INTERACTING FACTORs. The phyB mutant showed reduced expression of several fatty acid desaturase (FAD) genes, proportion of fully unsaturated fatty acids and electrolyte leakage of membranes exposed to a heat shock. Activation of phyB by red light also reduced thermotolerance of dark-grown (etiolated) seedlings but not via changes in FAD gene expression and membrane stability. We propose that the reduced photosynthetic capacity linked to thermotolerant membranes would be less costly under shade, where the light input itself limits photosynthesis.

plant biology↗