Aerial architecture in higher plants is dependent on the activity of the shoot apical meristem (SAM) and axillary meristems (AMs). The SAM produces a main shoot and leaf primordia, while AMs are generated at the axils of leaf primordia and give rise to branches and flowers. Therefore, the formation of AMs is a critical step in the construction of plant architecture. Here, we characterized the rice (Oryza sativa) lax panicle2 (lax2) mutant, which has altered AM formation. LAX2 regulates the branching of the aboveground parts of a rice plant throughout plant development, except for the primary branch in the panicle. The lax2 mutant is similar to lax panicle1 (lax1) in that it lacks an AM in most of the lateral branching of the panicle and has a reduced number of AMs at the vegetative stage. The lax1 lax2 double mutant synergistically enhances the reduced-branching phenotype, indicating the presence of multiple pathways for branching. LAX2 encodes a nuclear protein that contains a plant-specific conserved domain and physically interacts with LAX1. We propose that LAX2 is a novel factor that acts together with LAX1 in rice to regulate the process of AM formation.
高等植物的地上部分株型是由SAM（頂端分生組織）和AMs（腋生分生組織）共同決定的。前者產(chǎn)生主莖和葉原基，后者在葉原基的葉腋部位產(chǎn)生并逐漸形成分枝和花序，因此，腋生分生組織的形成是構建植物株型的關鍵步驟。我們在水稻突變體庫中發(fā)現(xiàn)一新稀穗突變體lax2，該突變體腋生分生組織發(fā)生變化，該LAX2只調(diào)控著水稻地上部分的分枝的發(fā)育，并沒有調(diào)控穗的一次枝梗的發(fā)育。lax2與lax1表型類似，它們大部分側(cè)生小穗缺乏腋分生組織且營養(yǎng)生長階段葉腋分生組織數(shù)目減少。lax1 lax2 雙突變體的稀穗表型增強，表明分枝存在多種調(diào)控途徑，LAX2編碼一個核蛋白，含有植物特異的保守結(jié)構域，能與LAX1蛋白互作。因此，我們認為LAX2是一個通過與LAX1相互作用一起參與調(diào)控水稻AM形成新的蛋白因子。