Abstract
Reductions in red to far-red ratio (R:FR) provide plants with an unambiguous signal of vegetational shade and are monitored by phytochrome photoreceptors. Plants integrate this information with other environmental cues to determine the proximity and density of encroaching vegetation. Shade-sensitive species respond to reductions in R:FR by initiating a suite of developmental adaptations termed shade avoidance. These include the elongation of stems to facilitate light foraging. Hypocotyl elongation is driven by increased auxin biosynthesis promoted by PHYTOCHROME INTERACTING FACTORs (PIF) 4, 5 and 7. UV-B perceived by the UV RESISTANCE LOCUS 8 (UVR8) photoreceptor rapidly inhibits shade avoidance, in part by suppressing PIF4/5 transcript accumulation and destabilising PIF4/5 protein. Here, we show that longer-term inhibition of shade avoidance is sustained by ELONGATED HYPOCOTYL 5 (HY5) and HY5 HOMOLOGUE (HYH), which regulate transcriptional reprogramming of genes involved in hormone signalling and cell wall modification. HY5 and HYH are elevated in UV-B and suppress the expression of XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE (XTH) genes involved in cell wall loosening. They additionally increase expression GA2-OXIDASE1 (GA2ox1) and GA2ox2, encoding gibberellin catabolism enzymes that act redundantly to stabilise the PIF-inhibiting DELLA proteins. UVR8 therefore regulates temporally distinct signalling pathways to first rapidly inhibit and subsequently maintain suppression of shade avoidance following UV-B exposure.
| Original language | English |
|---|---|
| Pages (from-to) | 1394-1407 |
| Number of pages | 14 |
| Journal | The Plant Journal |
| Volume | 115 |
| Issue number | 5 |
| Early online date | 27 May 2023 |
| DOIs | |
| Publication status | Published - 27 Aug 2023 |
Bibliographical note
Funding Information:RNA sequencing was performed by the Bristol Genomics Facility. The authors thank Tom Batstone and Alex Paterson (University of Bristol) for additional bioinformatics support. The authors declare no conflicts of interest. This work was funded by BBSRC grant numbers BB/M008711/1 and BB/R002045/1. AP was supported by a Leverhulme Trust Early Career Fellowship (ECF‐2022‐310) and the Bristol Centre for Agricultural Innovation.
Funding Information:
RNA sequencing was performed by the Bristol Genomics Facility. The authors thank Tom Batstone and Alex Paterson (University of Bristol) for additional bioinformatics support. The authors declare no conflicts of interest. This work was funded by BBSRC grant numbers BB/M008711/1 and BB/R002045/1. AP was supported by a Leverhulme Trust Early Career Fellowship (ECF-2022-310) and the Bristol Centre for Agricultural Innovation.
Publisher Copyright:
© 2023 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.
Keywords
- UV-B, shade avoidance, HY5, phytochrome, DELLA