COP1 regulates the stability of CAM7 to promote photomorphogenic growth

Abstract

The unique member of the calmodulin gene family, Calmodulin7 ( CAM 7), plays a crucial role as transcriptional regulator to promote Arabidopsis seedling development. CAM 7 regulates the expression of HY 5 , which is intimately involved in the promotion of photomorphogenic growth and light‐regulated gene expression. COP 1 ubiquitin ligase suppresses photomorphogenesis by degrading multiple photomorphogenesis promoting factors including HY 5 in darkness. Genetic interaction studies, in this report, reveal that CAM 7 and COP 1 co‐ordinately work to promote photomorphogenic growth and light‐regulated gene expression at lower intensity of light. CAM 7 physically interacts with COP 1 in the nucleus. Further, in vivo study suggests that CAM 7 and COP 1 interaction is light intensity dependent. We have also shown that functional COP 1 is required for optimum accumulation of CAM 7 at lower fluences of light. Taken together, this study demonstrates the coordinated function of CAM 7 and COP 1 in Arabidopsis seedling development.

The Z-box binding factors (ZBFs): emerging new facets in Arabidopsis seedling development

“…Although ZBFs were discovered as bona fide Z-box binding proteins, it is increasingly evident that they bind to several cis-acting elements present in the promoters of light, ABA and JA signaling pathway genes and regulate their expression (Boter et al 2004;Mallappa et al 2006;Dombrecht et al 2007;Godoy et al 2011;Singh et al 2012;Gangappa and Chattopadhyay 2013). The protein abundance and nucleo-cytoplasmic shuttling of ZBFs with their interacting partners during Arabidopsis seedling development appeared to be light dependent (Mallappa et al 2008;Kushwaha et al 2008;Senapati et al 2019). Moreover, the varied environmental light signals appear to be the basis for discrimination between different mode (monomer, homodimer, or heterodimer) of transcriptional regulation by the ZBFs (Singh et al 2012).…”

“…In a recent study, by using constitutive over-expresser transgenic lines of HY5, a feedback regulatory mechanism of HY5 has been proposed through COP1/SPA ubiquitin ligase system, which is known to degrade HY5 (Osterlund et al 2000;Burko et al 2020). CAM7 has recently been shown to be stabilized by COP1 at lower intensity of light for promoting photomorphogenic growth (Senapati et al 2019). Overexpression of CAM7 in cop1 mutants background enhanced the photomorphogenic growth and caused higher accumulation of chlorophyll and anthocyanin and increased expression of CAB1, RBCS-1A, and CHS1.…”

“…Overexpression of CAM7 in cop1 mutants background enhanced the photomorphogenic growth and caused higher accumulation of chlorophyll and anthocyanin and increased expression of CAB1, RBCS-1A, and CHS1. Owing to the fact that, (i) like COP1, CAM7 is localized to nucleus in dark but are present in nucleus as well as cytosol in light, (ii) CAM7 physically interacts with COP1 at lower fluence of WL, and (iii) accumulation of CAM7 was reduced in CAM7OE cop1-4 background as compared to CAM7OE lines in WL grown seedlings, it is postulated that COP1 is required for the optimum accumulation of CAM7 at lower intensity of WL (Von Arnim and Deng 1996;Lau and Deng 2012;Huang et al 2014;Senapati et al 2019 and Fig. 1).…”

“…Expression of GBF1 also strongly increased during seed germination (Iglesias-Fernández et al 2014). Apart from playing a predominant role in seedling development, the ZBFs have been demonstrated to influence various other developmental processes such as seed germination, root growth, flowering time and senescence (Yadav et al 2005;Mallappa et al 2006;Gangappa et al 2010;Gangappa and Chattopadhyay 2010;Senapati et al 2019). Furthermore, ZBFs also cross-talk with ABA, JA, EL and CK signaling pathways to influence diverse signaling processes (Yadav et al 2005;Kazan and Manners 2013;Gangappa et al 2013b;Zhang et al 2014;Shrivastava et al 2019;Zhuo et al 2019 and Fig.…”

MKKK20 works as an upstream triple-kinase of MKK3-MPK6-MYC2 module in Arabidopsis seedling development

“…It has been shown by a protein microarray study that MKKK20 is able to interact with Calmodulin 7 (CAM7), which is a key transcription factor involved in light signaling pathways. 29 , 30 , 31 , 32 , 33 Further studies have revealed that whereas MPK6 works downstream of MKKK20 in the regulation of osmotic stress, 34 MKKK20 works upstream to MKK3 in the regulation of root growth. 35 The involvement of MKKK20 has been shown in ABA responses.…”