Abstract
TAC1 and LAZY1 are members of a gene family that regulates lateral shoot orientation in plants. TAC1 promotes outward orientations in response to light, while LAZY1 promotes upward shoot orientations in response to gravity via altered auxin transport. We performed genetic, molecular, and biochemical assays to investigate possible interactions between these genes. In Arabidopsis they were expressed in similar tissues and double mutants revealed the wide-angled lazy1 branch phenotype, indicating it is epistatic to the tac1 shoot phenotype. Surprisingly, the lack of TAC1 did not influence gravitropic shoot curvature responses. Combined, these results suggest TAC1 might negatively regulate LAZY1 to promote outward shoot orientations. However, additional results revealed that TAC1- and LAZY1 influence on shoot orientation is more complex than a simple direct negative regulatory pathway. Transcriptomes of Arabidopsis tac1 and lazy1 mutants compared to wild type under normal and gravistimulated conditions revealed few overlapping differentially expressed genes. Overexpression of each gene did not result in major branch angle differences. Shoot tip hormone levels were similar between tac1, lazy1, and Col, apart from exceptionally elevated levels of salicylic acid in lazy1. The data presented here provide a foundation for future study of TAC1 and LAZY1 regulation of shoot architecture.
Highlights
Lateral organ orientation in both shoots and roots plays a key role in a plant’s interaction with the environment and its ability to access resources such as light and water
Little to no expression was observed in mature promAtTAC::GUS and promAtLAZY1::GUS rosette leaves, but signal was present in rosette petioles as well as younger leaves to varying degrees (Fig. C-F; Supplementary Figures S1 and S2)
TILLER ANGLE CONTROL 1 (TAC1), which is upregulated in response to light, promotes outward shoot orientations
Summary
Lateral organ orientation in both shoots and roots plays a key role in a plant’s interaction with the environment and its ability to access resources such as light and water. The IGT gene family members TILLER ANGLE CONTROL 1 (TAC1) and the related set of LAZY genes are important regulators of lateral organ orientation[1,2]. These genes share four conserved amino acid regions or domains, and LAZY genes share an additional C-terminal domain[3,4]. Plants with multiple lazy/dro mutations exhibit even wider lateral shoot/root angles and, in some cases, downward shoot growth and/or upward root growth[7,8,10,11] Together, those findings demonstrate that TAC1 promotes horizontal lateral organ orientations, while LAZY genes promote vertical orientations. The EAR motif mediated interactions between wheat LAZY4/DRO1 protein and auxin signaling repressor TOPLESS, suggesting it is functional in this species[11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
