Molecular pathways regulating elongation of aerial plant organs: a focus on light, the circadian clock, and temperature

Abstract

Summary Organs such as hypocotyls and petioles rapidly elongate in response to shade and temperature cues, contributing to adaptive responses that improve plant fitness. Growth plasticity in these organs is achieved through a complex network of molecular signals. Besides conveying information from the environment, this signaling network also transduces internal signals, such as those associated with the circadian clock. A number of studies performed in Arabidopsis hypocotyls, and to a lesser degree in petioles, have been informative for understanding the signaling networks that regulate elongation of aerial plant organs. In particular, substantial progress has been made towards understanding the molecular mechanisms that regulate responses to light, the circadian clock, and temperature. Signals derived from these three stimuli converge on the BAP module, a set of three different types of transcription factors that interdependently promote gene transcription and growth. Additional key positive regulators of growth that are also affected by environmental cues include the CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and SUPPRESSOR OF PHYA‐105 (SPA) E3 ubiquitin ligase proteins. In this review we summarize the key signaling pathways that regulate the growth of hypocotyls and petioles, focusing specifically on molecular mechanisms important for transducing signals derived from light, the circadian clock, and temperature. While it is clear that similarities abound between the signaling networks at play in these two organs, there are also important differences between the mechanisms regulating growth in hypocotyls and petioles.

Molecular GA pathways as conserved integrators for adaptive responses

“…It is then obvious that phytohormones inevitably interfere with one another, as they target common processes of plant development. DELLA interactions with key regulators of hormone pathways highlight interactions with GA, BR and auxin signalling to regulate cell elongation (Davi ere Franciosini et al 2017;Bour e et al 2019;Favero et al 2021). For instance, DELLA proteins bind to AUXIN RESPONSE FACTOR 6 (ARF6) and BRASSINAZOLE RESISTANT 1 (BZR1) to modulate auxin and BR responses, respectively (Bai et al 2012;Oh et al 2014).…”

“…2019; Favero et al . 2021). For instance, DELLA proteins bind to AUXIN RESPONSE FACTOR 6 (ARF6) and BRASSINAZOLE RESISTANT 1 (BZR1) to modulate auxin and BR responses, respectively (Bai et al .…”

Integration of mRNA and miRNA analysis reveals the differentially regulatory network in two different Camellia oleifera cultivars under drought stress

“…The Phytochrome Interacting Factor (PIF) is a small subset of basic helix-loop-helix TFs that function as a cellular signaling hub, integrating internal and external stimuli to coordinate the regulation of the transcriptional network that drives multiple morphogenic responses (Leivar and Quail, 2011). The PIF4, PIF5, and PIF7 have been shown that act as clock output controlled by circadian clock genes that manipulated plant growth and development (Cheng et al, 2021;Favero et al, 2021). It is reported that PIF7 negatively regulates DREB1 expression under circadian control in Arabidopsis, consequently repressed DREB1 expression may be important for avoiding plant growth retardation under unstressed conditions.…”

Abscisic acid modulates auxin-responsive hypocotyl elongation

“…In addition, we examined transcript accumulation from genes that have been directly or indirectly associated with promoting or inhibiting hypocotyl elongation (Supplemental File 3), including genes involved in the biosynthesis, catabolism, or signaling of plant hormones implicated in regulating hypocotyl elongation such as GA and brassinosteroids, genes implicated in cell wall remodeling or acidification, and other genes that have been experimentally implicated in regulating hypocotyl elongation (24,36,37). Notably, several genes with known roles in hypocotyl elongation regulation display ABA-dependent regulation in dark-grown hypocotyls (Table 1).…”