背景回顾：The flattened leaf form is an important adaptation for efficient photosynthesis, and the developmental process of flattened leaves has been intensively studied. Classic microsurgery studies in potato and tomato suggest that the shoot apical meristem (SAM) communicates with the leaf primordia to promote leaf blade formation. More recently, it was found that polar auxin transport (PAT) could mediate this communication. 

提出问题：However, it is unclear how the expression of leaf patterning genes is tailored by PAT routes originating from SAM. 

主要发现：By combining experimental observations and computer model simulations, we show that microsurgical incisions and local inhibition of PAT in tomato interfere with auxin transport toward the leaf margins, reducing auxin response levels and altering the leaf blade shape. 

结果1-LAM1和REV：Importantly, oval auxin responses result in the bipolar expression of SlLAM1 that determines leaf blade formation. Furthermore, wounding caused by incisions promotes degradation of SlREV, a known regulator of leaf polarity. 

结果2-局域生长素合成：Additionally, computer simulations suggest that local auxin biosynthesis in early leaf primordia could remove necessity for external auxin supply originating from SAM, potentially explaining differences between species. 

结论：Together, our findings establish how PAT near emerging leaf primordia determines spatial auxin patterning and refines SlLAM1 expression in the leaf margins to guide leaf flattening.

扁平的叶形式是植物以便高效光合作用的适应性性状，有关这一性状的发育过程已经有了深入和研究。在马铃薯和番茄中的相关研究表明，茎尖分生组织（SAM）与叶原基之间的通信促进片状叶的形成。最近，有研究报道了极性生长素运输（PAT）可能介导了这一通信。但是，尚不清楚叶模式建成基因的表达是如何受到来自SAM的PAT途径的调控的。通过结合试验观察和电脑建模模拟，作者发现显微切口和PAT的局部抑制会干扰番茄中生长素向叶边缘的运输，降低生长素的响应水平并改变叶片形状。重要的是，椭圆形生长素响应导致了叶片形成决定基因SlLAM1的双极性表达。此外，切口导致的创伤会促进叶片极性调控因子SlREV的降解。同时，电脑建模模拟显示，在早期叶原基中的局域生长素生物合成能够消除后期来自SAM等外部生长素供应的必要性，这潜在解释了物种间的差异。综上，本文的研究结果确立了新形成的叶原基附近的PAT如何决定空间生长素模式以及叶片边缘SlLAM1的表达，最终指导叶扁平化。

** 焦雨铃 **