IGT/LAZY family genes are differentially influenced by light signals and collectively required for light-induced changes to branch angle

Abstract

Plants adjust their growth orientations in response to environmental signals such as light and gravity in order to optimize photosynthesis and access to nutrients. However, given the fixed nature of gravity, understanding how light and gravity signals are integrated is challenging. Branch orientation, or gravitropic set point angle, is a key aspect of plant architecture, set with respect to gravity and shown to be altered by changes in light conditions. The IGT gene family, also known as the LAZY family, contains important components for branch angle and gravity responses, including three gene clades: LAZY, DEEPER ROOTING (DRO), and TILLER ANGLE CONTROL (TAC). LAZY and DRO genes promote upward branch orientations downstream of amyloplast sedimentation, and upstream of auxin redistribution in response to gravity. In contrast, TAC1 promotes downward branch angles in response to photosynthetic signals. Here, we investigated the influence of different light signaling pathways on LAZY and DRO gene expression, and their role in light regulation of branch angle responses. We found differential effects of continuous light and dark, circadian clock, photoreceptor-mediated signaling, and photosynthetic signals on LAZY and DRO gene expression. Phenotypic analysis revealed that LAZY and DRO genes are collectively required for branch angle responses to light.HighlightLAZY and DRO gene expression responds differentially to changes in light regime and signaling. Loss of multiple LAZY and DRO genes leads to loss of branch angle response to light.

QTL mapping of the narrow-branch “Pendula” phenotype in Norway spruce (Picea abies L. Karst.)

“…and LG V (WEEP2, MA_10435286g0010). The IGT gene family, which harbors several genes known to influence plant architecture in angiosperms, including LAZY, TAC (Tillar angle control) and DRO (Deeper rooting) (Hollender, Waite, et al, 2018;Jiao et al, 2021;Waite & Dardick, 2020), appears to be a single copy gene in P. abies as we can only identify a single homolog, MA_39199g0010. This gene is positioned at the distal ends of LG I.. 19 of the gene models, from 10 different gene families, are located on LG VI.…”

“…The WEEP genes that have been found to yield a pendulous phenotype in peach ( Prunus persica ) to (Hollender, Waite, et al, 2018) are positioned on LG X ( WEEP1 , MA_181281g0010) and LG V ( WEEP 2, MA_10435286g0010). The IGT gene family, which harbors several genes known to influence plant architecture in angiosperms, including LAZY , TAC ( Tillar angle control ) and DRO ( Deeper rooting ) (Hollender, Waite, et al, 2018; Jiao et al, 2021; Waite & Dardick, 2020), appears to be a single copy gene in P. abies as we can only identify a single homolog, MA_39199g0010. This gene is positioned at the distal ends of LG I.…”

Restructuring plant types for developing tailor‐made crops

“…Light‐directed orientation of branch angle through LZY1 is also reported recently. Both photosynthetic signals and photoreceptors influence the expression of LZY1 (Waite and Dardick, 2020). The crossover between light and gravitropic signalling is also evident from the modulation of LZY4 expression in root and hypocotyl of Arabidopsis through the accumulation of ELONGATED HYPOCOTYL 5 (HY5) and degradation of PHYTOCHROME INTERACTING FACTOR (PIF) proteins, respectively (Yang et al ., 2020).…”

Tiller Angle Control 1 Is Essential for the Dynamic Changes in Plant Architecture in Rice

“…However, it retained a loose plant architecture with a relatively larger tiller angle throughout its growth under NSD conditions (Figure 1e-h). TAC1 encodes an expressed protein, which belongs to the IGT gene family, that also includes LAZY and DEEPER ROOTING (DRO) genes [8,50]. In Arabidopsis, LAZY1, LAZY6, DRO1, DRO2, and AtTAC1 are involved in the circadian clock, and are collectively required for light-mediated branch angle orientation [50,51].…”

“…TAC1 encodes an expressed protein, which belongs to the IGT gene family, that also includes LAZY and DEEPER ROOTING (DRO) genes [8,50]. In Arabidopsis, LAZY1, LAZY6, DRO1, DRO2, and AtTAC1 are involved in the circadian clock, and are collectively required for light-mediated branch angle orientation [50,51]. For example, light promotes AtTAC1 expression, while dark inhibits its expression, which leads to narrower lateral branch angles in response to growth in continuous dark versus light [51].…”