The Multifaceted Roles of HY5 in Plant Growth and Development

Abstract

ELONGATED HYPOCOTYL5 (HY5), a member of the bZIP transcription factor family, inhibits hypocotyl growth and lateral root development, and promotes pigment accumulation in a light-dependent manner in Arabidopsis. Recent research on its role in different processes such as hormone, nutrient, abiotic stress (abscisic acid, salt, cold), and reactive oxygen species signaling pathways clearly places HY5 at the center of a transcriptional network hub. HY5 regulates the transcription of a large number of genes by directly binding to cis-regulatory elements. Recently, HY5 has also been shown to activate its own expression under both visible and UV-B light. Moreover, HY5 acts as a signal that moves from shoot to root to promote nitrate uptake and root growth. Here, we review recent advances on HY5 research in diverse aspects of plant development and highlight still open questions that need to be addressed in the near future for a complete understanding of its function in plant signaling and beyond.

Two B-Box Proteins Regulate Photomorphogenesis by Oppositely Modulating HY5 through their Diverse C-Terminal Domains

“…HY5 action is further modulated by a number of other factors (Gangappa and Botto, 2016). In this study,…”

Light Signaling, Root Development, and Plasticity

“…The transcription factor HY5 is a key integrator of photomorphogenesis and is involved in light, hormone, and stress signaling (Cluis et al, 2004;Lee et al, 2007;Gangappa and Botto, 2016). HY5 was recently shown to be transported upon light activation from the shoot to the root (Chen et al, 2016).…”

“…photomorphogenesis, and it serves as the center of a transcriptional network hub of hormone and light signaling (Gangappa and Botto, 2016). Besides HY5, COP1 also targets factors like the MYB transcription factor LONG AFTER FAR-RED LIGHT1 (Seo et al, 2003), the basic helix-loop-helix protein LONG HY-POCOTYL IN FAR-RED1 (Duek et al, 2004), and even phytochrome A (phyA) and phyB photoreceptors (Seo et al, 2004;Jang et al, 2010).…”

A Rice B-Box Protein, OsBBX14, Finely Regulates Anthocyanin Biosynthesis in Rice

“…In Arabidopsis , ELONGATED HYPOCOTYL 5 (HY5) is considered as a key signaling player in photomorphogenesis, and directly activates the expression of the R2R3-MYB TF, production of anthocyanin pigment 1 ( PAP1 ) and anthocyanin biosynthesis genes, chalcone synthase ( CHS ), and chalcone isomerase ( CHI ) by binding to their promoters [14,17]. Several studies have therefore shown that genes controlling HY5 can positively and negatively regulate anthocyanin biosynthesis [18,19]. …”

“…B-box proteins (BBX), which contain one or two B-box domains at their N-terminal region, function as TFs and have roles in plant growth and development [18]. The BBX proteins are classified into five subfamilies based on their phylogeny and domain compositions in Arabidopsis and rice [20,21].…”