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.

TAC1和LAZY1是调节植物侧枝方向的基因家族的成员。TAC1响应光促进外向定向，而LAZY1通过改变生长素转运而响应重力促进向上射向。我们进行了遗传，分子和生化分析，以研究这些基因之间可能的相互作用。在拟南芥中，它们在相似的组织中表达，双突变体揭示了广角的lazy1分支表型，表明它对tac1芽表型具有上位性。出人意料的是，缺乏TAC1不会影响重力射影曲率响应。综合来看，这些结果表明TAC1可能会对LAZY1产生负调控，以促进向外芽的方向。但是，其他结果表明，TAC1-和LAZY1对芽取向的影响比简单的直接负调控途径更为复杂。与野生型相比，拟南芥tac1和lazy1突变体的转录组在正常和去刺激条件下均显示很少重叠的差异表达基因。每个基因的过表达并没有导致主要的分支角差异。茎尖激素水平之间相似TAC1，lazy1从水杨酸异常升高的水平，和Col，除了lazy1。这里提供的数据为TAC1和LAZY1芽构型调控的未来研究提供了基础。