The microRNA miR319 and its target JAW-TCP transcription factors regulate the proliferation-to-differentiation transition of leaf pavement cells in diverse plant species. In young Arabidopsis leaf primordia, JAW-TCPs are detected towards the distal region whereas the major mRNA319-encoding gene MIR319C, is expressed at the base. Little is known about how this complementary expression pattern of MIR319C and JAW-TCPs is generated. Here, we show that MIR319C is initially expressed uniformly throughout the incipient primordia and is later abruptly down-regulated at the distal region, with concomitant distal appearance of JAW-TCPs, when leaves grow to ~100 μm long. Loss of JAW-TCPs causes distal extension of the MIR319C expression domain, whereas ectopic TCP activity restricts MIR319C more proximally. JAW-TCPs are recruited to and are capable of depositing histone H3K27me3 repressive marks on the MIR319C chromatin. JAW-TCPs fail to repress MIR319C in transgenic seedlings where the TCP-binding cis-elements on MIR319C are mutated, causing miR319 gain-of-function-like phenotype in the embryonic leaves. Based on these results, we propose a model for growth patterning in leaf primordia wherein MIR319C and JAW-TCPs repress each other and divide the uniformly growing primordia into distal differentiation zone and proximal proliferation domain.

中文翻译：

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miR319c 和 JAW-TCP 之间的双负反馈环建立了拟南芥早期叶原基的生长模式。

microRNA miR319 及其靶标 JAW-TCP 转录因子调节不同植物物种叶面细胞的增殖到分化转变。在年轻的拟南芥叶原基中，JAW-TCP 在远端区域检测到，而主要 mRNA319 编码基因 MIR319C 在基部表达。关于 MIR319C 和 JAW-TCP 的这种互补表达模式是如何产生的，人们知之甚少。在这里，我们表明，MIR319C 最初在整个初期原基中均匀表达，随后当叶子长到约 100 μm 长时，在远端区域突然下调，并伴随 JAW-TCP 的远端出现。JAW-TCP 的丢失会导致 MIR319C 表达域向远端延伸，而异位 TCP 活性则限制 MIR319C 的近端表达。JAW-TCP 被招募并能够在 MIR319C 染色质上沉积组蛋白 H3K27me3 抑制标记。JAW-TCP 无法抑制转基因幼苗中的 MIR319C，其中 MIR319C 上的 TCP 结合顺式元件发生突变，导致胚叶中出现 miR319 功能获得样表型。基于这些结果，我们提出了叶原基生长模式的模型，其中 MIR319C 和 JAW-TCP 相互抑制，并将均匀生长的原基分为远端分化区和近端增殖区。