• The patterning of adaxial–abaxial tissues plays a vital role in the morphology of lateral organs, which is maintained by antagonism between the genes that specify adaxial and abaxial tissue identity. The homeo-domain leucine zipper class III (HD-ZIP III) family genes regulate adaxial identity; however, little information is known about the physical interactions or transcriptionally regulated downstream genes of HD-ZIP III.
• In this study, we identified a dominant rice mutant, lateral floret 1 (lf1), which has defects in lateral organ polarity. LF1 encodes the HD-ZIP III transcription factor, which expressed in the adaxial area of lateral organs.
• LF1 can activate directly the expression of LITTLE ZIPPER family gene OsZPR4 and HD-ZIP II family gene OsHOX1, and OsZPR4 and OsHOX1 respectively interact with LF1 to form a heterodimer to repress the transcriptional activity of LF1. LF1 influences indole-3-acetic acid (IAA) content by directly regulating the expression of OsYUCCA6. Therefore, LF1 forms negative feedback loops between OsZPR4 and OsHOX1 to affect IAA content, leading to the regulation of lateral organs polarity development.
• These results reveal the cross-talk among HD-ZIP III, LITTLE ZIPPER, and HD-ZIP II proteins and provide new insights into the molecular mechanisms underlying the polarity development of lateral organs.

中文翻译：

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LF1调节水稻侧向器官极性发育

• 近轴 - 远轴组织的模式在侧向器官的形态中起着至关重要的作用，这是通过指定近轴和远轴组织同一性的基因之间的拮抗作用来维持的。同源域亮氨酸拉链 III 类 (HD-ZIP III) 家族基因调节近轴特性；然而，关于 HD-ZIP III 的物理相互作用或转录调控的下游基因的信息知之甚少。
• 在这项研究中，我们鉴定了一个显性水稻突变体侧向小花 1 ( lf1 )，其侧向器官极性存在缺陷。LF1编码 HD-ZIP III 转录因子，它在横向器官的近轴区域表达。
• LF1可以直接激活LITTLE ZIPPER家族基因OsZPR4和HD-ZIP II家族基因OsHOX1的表达，OsZPR4和OsHOX1分别与LF1相互作用形成异二聚体抑制LF1的转录活性。LF1 通过直接调节OsYUCCA6的表达来影响吲哚-3-乙酸 (IAA) 的含量。因此，LF1 在 OsZPR4 和 OsHOX1 之间形成负反馈回路，影响 IAA 含量，从而调节侧向器官极性发展。
• 这些结果揭示了 HD-ZIP III、LITTLE ZIPPER 和 HD-ZIP II 蛋白之间的串扰，并为侧向器官极性发展的分子机制提供了新的见解。