Biology subjects

Paulisic, S.

Publications and source records attributed to Paulisic, S..

4 recordsLinked to original sources

bioRxiv2026

Internal sugar allocation in response to a shade signal is regulated by concerted action of auxin and sucrose

Plants detect proximity to neighboring vegetation by light spectral signatures which are sensed by phytochrome photoreceptors. As a response, many species grow taller to out-compete their neighbors. In seedlings, the rapid elongation of hypocotyls requires enhanced supply of carbon resources from the cotyledons, transported as sucrose. The mechanisms of how phytochrome signaling regulates carbon allocation are unknown. We show that sucrose biosynthesis, particularly the step catalyzed by sucrose phosphate synthase (SPS), is a key determinant of hypocotyl elongation. Moreover, we show that auxin directs resource allocation to the elongating hypocotyl. Increased sucrose availability enhances elongation only when auxin levels are sufficient, highlighting the interdependence between sugar supply and auxin. In contrast, our data reveal that reduced sucrose availability does not impair neighbor-proximity-induced auxin synthesis and signaling in hypocotyls and cotyledons. Our findings shed light on the regulation of carbon allocation -- a process which is poorly understood, despite its importance for crop yield.

plant biology↗

bioRxiv2025

Transcriptional Dynamics and Chromatin Accessibility in the Regulation of Shade-Responsive Genes in Arabidopsis

Open chromatin regions host DNA regulatory motifs that are accessible to transcription factors and the transcriptional machinery. In Arabidopsis, responses to light are heavily regulated at the transcriptional level. Shade, for example, can limit photosynthesis and is rapidly perceived by phytochromes as a reduction of red to far-red light ratio (LRFR). Under shade, phytochromes become inactive, enabling PHYTOCHROME INTERACTING FACTORs (PIFs), particularly PIF7, to promote genome-wide reprogramming essential for LRFR responses. An initial strong and fast regulation of shade-responsive genes is followed by attenuation of this response under prolonged shade. We wanted to determine whether the transcriptional response to shade depends on chromatin accessibility. For this, we used ATAC-seq to profile the chromatin of seedlings exposed to short (1h) and long (25h) simulated shade. We found that PIF7 binding sites were accessible for most early target genes before LRFR treatment. The transcription pattern of most acute shade-responsive genes correlated with a rapid increase in PIF levels and chromatin association at 1h, and its decrease at 25h of shade exposure. For a small subset of acutely responding genes, PIFs also modulate chromatin accessibility at their binding sites early and/or late in the response to shade. Our results suggest that in seedlings a state of open chromatin conformation allows PIFs to easily access and recognize their binding motifs, rapidly initiating gene expression triggered by shade. This transcriptional response primarily depends on a transient increase in PIF stability and gene occupancy, accompanied by changes in chromatin accessibility in a minority of genes.

plant biology↗

bioRxiv2020

Light quality signals generated by vegetation shade facilitate acclimation to reduced light quantity in shade-avoider plants

O_LIWhen growing in search for light, plants can experience continuous or occasional shading by other plants. Plant proximity causes a decrease in the ratio of red to far red light (low R:FR) due to the preferential absorbance of red light and reflection of far red light by photosynthetic tissues of neighboring plants. This signal is often perceived before actual shading causes a reduction in photosynthetically active radiation (low PAR). C_LIO_LIHere we investigated elongation, photosynthesis and photoacclimation responses in several Brassicaceae species to explore the possible connections between low R:FR and low PAR. C_LIO_LIA negative correlation was found in shade-tolerant Cardamine hirsuta and shade-avoider Arabidopsis thaliana seedlings (e.g., shade-tolerance was associated with a good adaptation to low PAR but a poor or null response to low R:FR exposure). However, they could be genetically uncoupled. Most interestingly, exposure to low R:FR of shade-avoider plants improved their photoacclimation to low PAR by triggering changes in photosynthesis-related gene expression, pigment accumulation and chloroplast ultrastructure. C_LIO_LIThese results indicate that low R:FR signaling unleashes molecular, metabolic and developmental responses that allow shade-avoider plants (including most crops) to adjust their photosynthetic capacity in anticipation of eventual shading by nearby plants. C_LI

plant biology↗

bioRxiv2020

Adaptation to plant shade relies on rebalancing the transcriptional activity of the PIF-HFR1 regulatory module

Shade caused by the proximity of neighboring vegetation triggers a set of acclimation responses to either avoid or tolerate shade. Comparative analyses between the shade avoider Arabidopsis thaliana and the shade tolerant Cardamine hirsuta, revealed a role for the atypical basic-helix-loop-helix LONG HYPOCOTYL IN FR 1 (HFR1) in maintaining the shade-tolerance in C. hirsuta, inhibiting hypocotyl elongation in shade and constraining expression profile of shade induced genes. We showed that C. hirsuta HFR1 protein is more stable than its A. thaliana counterpart, contributing to enhance its biological activity. The enhanced HFR1 activity is accompanied by an attenuated PHYTOCHROME INTERACTING FACTOR (PIF) activity in C. hirsuta. As a result, the PIF-HFR1 module is imbalanced, causing a reduced PIF activity and attenuating other PIF-mediated responses such as warm temperature-induced hypocotyl elongation (thermomorphogenesis) and dark-induced senescence. By this mechanism and that of the already-known of phytochrome A photoreceptor, plants might ensure to properly adapt and thrive in habitats with disparate light amounts.

plant biology↗