IGT/LAZY genes are differentially influenced by light and required for light-induced change to organ angle

Authors: Waite, Jessica; Dardick, Christopher - Chris

Submitted to: BMC Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plants constantly adjust the growth of their organs by responding to environmental signals, such that they can reach crucial nutrients like light, water, and nutrients. To do this, plant organs respond to signals including light, gravity, and moisture to tell them where to grow. Understanding how plants respond to each of these signals, and also how these signals are sensed together, is important for improving plant growth and survival. A family of genes, called the IGT gene family, have been shown to be important for setting branch and root growth angles in response to gravity. We recently showed that one of these genes is also important for setting branch growth angles in response to light and photosynthesis, which may be one way that plants coordinate light and gravity cues. The current research shows that specific IGT genes respond to different types of light signals and that multiple genes are necessary for branch angle response to light. The research suggests the whole family of genes is important for determining organ growth angles in response to both light and gravity. This is important for informing future horticultural practices and breeding strategies, for example, achieving a better understanding of pruning and training rules, or potential development of breeding markers.

Technical Abstract: Plants adjust their growth orientations primarily in response to light and gravity signals. Considering that the gravity vector is fixed and the angle of light incidence is constantly changing, plants must somehow integrate these signals to establish organ orientation, commonly referred to as gravitropic set point angle (GSA). The IGT gene family contains known regulators of GSA, including the gene clades LAZY, DEEPER ROOTING (DRO), and TILLER ANGLE CONTROL (TAC). Results Here, we investigated the influence of light on different aspects of GSA phenotypes in LAZY and DRO mutants, as well as the influence of known light signaling pathways on IGT gene expression. Phenotypic analysis revealed that LAZY and DRO genes are collectively required for changes in the angle of shoot branch tip and root growth in response to light. Single lazy1 mutant branch tips turn upward in the absence of light and in low light, similar to wild-type, and mimic triple and quadruple IGT mutants in constant light and high-light conditions, while triple and quadruple IGT/LAZY mutants show little to no response to changing light regimes. Further, expression of IGT/LAZY genes is differentially influenced by daylength, circadian clock, and light signaling. Conclusions Collectively the data show that differential expression of LAZY and DRO genes are required to enable plants to alter organ angles in response to light-mediated signals.