Photoreceptors Regulate Plant Developmental Plasticity through Auxin

Abstract

Light absorption by plants changes the composition of light inside vegetation. Blue (B) and red (R) light are used for photosynthesis whereas far-red (FR) and green light are reflected. A combination of UV-B, blue and R:FR-responsive photoreceptors collectively measures the light and temperature environment and adjusts plant development accordingly. This developmental plasticity to photoreceptor signals is largely regulated through the phytohormone auxin. The phytochrome, cryptochrome and UV Resistance Locus 8 (UVR8) photoreceptors are inactivated in shade and/or elevated temperature, which releases their repression of Phytochrome Interacting Factor (PIF) transcription factors. Active PIFs stimulate auxin synthesis and reinforce auxin signalling responses through direct interaction with Auxin Response Factors (ARFs). It was recently discovered that shade-induced hypocotyl elongation and petiole hyponasty depend on long-distance auxin transport towards target cells from the cotyledon and leaf tip, respectively. Other responses, such as phototropic bending, are regulated by auxin transport and signalling across only a few cell layers. In addition, photoreceptors can directly interact with components in the auxin signalling pathway, such as Auxin/Indole Acetic Acids (AUX/IAAs) and ARFs. Here we will discuss the complex interactions between photoreceptor and auxin signalling, addressing both mechanisms and consequences of these highly interconnected pathways.

Plant Hormone-Mediated Regulation of Heat Tolerance in Response to Global Climate Change

“…As an adaptive response to higher ambient temperatures, plants exhibit dramatic morphological and architectural changes termed thermomorphogenesis. The phytohormone auxin plays an important role in heat stress-induced thermomorphogenesis, including stem (hypocotyl) elongation and leaf hyponasty ( Küpers et al, 2020 ). The heat-induced growth response is drastically restrained in auxin signaling mutants or transgenic plants expressing the bacterial IAA-lysine synthase ( iaaLys ) gene, which contains a relatively lower level of free IAA ( Gray et al, 1998 ).…”

“…Phytohormones are the endogenous signal molecules that play an important role in almost every aspect of plant development, growth, and defense processes ( Verma et al, 2016 ; Kumar et al, 2019 ; Emenecker and Strader, 2020 ; Jang et al, 2020 ; Küpers et al, 2020 ). In recent years, studies have found that exogenous application of phytohormones significantly ameliorated heat-induced damage and improved plant heat tolerance, which indicates that phytohormones actively participate in plant response to heat stress.…”

Effects of Elevated Temperature on Root System Development of Two Lupine Species

“…The vertical orientation of emerging roots is typically the first response of plants to gravity [40,41]. Sensing of the gravity stimulus ultimately triggers a signaling network orchestrated by the phytohormone auxin, which is key to the coordination of directional root growth in response to gravity [42][43][44]. Although root gravitropism has been studied extensively, no conclusive data on the onset of gravisensing is established.…”

Heat Stress Targeting Individual Organs Reveals the Central Role of Roots and Crowns in Rice Stress Responses

“…The significant increase in the leaf auxin content under HS-WP and HS-L conditions ( Figure 5 ) is consistent with the reported HS stimulation of the YUCCA auxin biosynthetic genes ( Feraru et al, 2019 ). IAA plays an important role in HS-induced thermomorphogenesis, especially leaf hyponasty as well as stem/hypocotyl elongation ( Küpers et al, 2020 ; Li et al, 2021 ). Moreover, auxin signalling is promoted by negative effect of HS on the levels of PILS6 protein, auxin carrier implicated in intracellular auxin distribution, which limits nuclear auxin availability ( Feraru et al, 2019 ).…”