Cryptochromes Interact Directly with PIFs to Control Plant Growth in Limiting Blue Light

Abstract

SUMMARY Sun-loving plants have the ability to detect and avoid shading through sensing of both blue and red light wavelengths. Higher plant cryptochromes (CRYs) control how plants modulate growth in response to changes in blue light. For growth under a canopy, where blue light is diminished, CRY1 and CRY2 perceive this change and respond by directly contacting two bHLH transcription factors, PIF4 and PIF5. These factors are also known to be controlled by phytochromes, the red/far-red photoreceptors; however, transcriptome analyses indicate that the gene regulatory programs induced by the different light wavelengths are distinct. Our results indicate that CRYs signal by modulating PIF activity genome-wide, and that these factors integrate binding of different plant photoreceptors to facilitate growth changes under different light conditions.

Neighbor Detection Induces Organ-Specific Transcriptomes, Revealing Patterns Underlying Hypocotyl-Specific Growth

“…Hence, despite the limited importance attributed to auxin in etiolated hypocotyl elongation (Gray et al, 1998), the hypocotyl growth programs in etiolated seedlings and in shade-treated green seedlings appear to be more similar than previously anticipated (Figure 7; Supplemental Figure 7). The XTH family of cell wall-modifying enzymes is involved in shade responses (Keuskamp et al, 2011;de Wit et al, 2015;Pedmale et al, 2016). The expression of several members of this family is selectively induced in hypocotyls, which is consistent with their growthpromoting roles (Figure 7; Supplemental Figure 7).…”

“…Notably, the expression of XTH (XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE) genes regulated by PIFs and/or IAA and/or BL has been linked to growth promotion (Hornitschek et al, 2009;Sasidharan et al, 2010;Keuskamp et al, 2011;de Wit et al, 2015;Pedmale et al, 2016). Our organ-specific analysis allowed us to test whether shade-induced expression of XTH genes selectively occurred in the fast growing hypocotyl.…”

“…Shade-regulated expression of many gene families encoding cell wall components or modifying enzymes has been observed before (Hornitschek et al, 2009;Keuskamp et al, 2011;Pedmale et al, 2016) (Supplemental Data Set 5). Notably, the expression of XTH (XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE) genes regulated by PIFs and/or IAA and/or BL has been linked to growth promotion (Hornitschek et al, 2009;Sasidharan et al, 2010;Keuskamp et al, 2011;de Wit et al, 2015;Pedmale et al, 2016).…”

“…The phytochrome (phy) photoreceptors play a crucial role in shade and neighbor perception, with phyB having a predominant function in the model plant Arabidopsis thaliana (Franklin and Quail, 2010). The reduction in blue light typical of true shade is sensed by the cryptochrome photoreceptors (Sellaro et al, 2010;Keller et al, 2011;Pedmale et al, 2016). In young seedlings, cotyledons are considered to be the primary site of low R/FR perception; nevertheless, several studies have shown that other parts of the plant can also sense this light cue (Morgan et al, 1980;Tanaka et al, 2002;Procko et al, 2014;Nito et al, 2015).…”

Diverse photoreceptors and light responses in plants

“…Some signaling proteins correlate with each other so that many responses are redundantly regulated by different photoreceptors. Crosstalk in signaling pathways downstream of phy and cry are found in de-etiolation and flowering (Endo et al 2016;Pedmale et al 2016). A complicated network of light signaling from each photoreceptor evolved enabling a response against changes in light environment.…”