Polarity formation is central to leaf morphogenesis, and several key genes that function in adaxial-abaxial polarity establishment have been identified and characterized extensively. We previously reported that Arabidopsis thaliana ASYMMERTIC LEAVES1 (AS1) and AS2 are important in promoting leaf adaxial fates. We obtained an as2 enhancer mutant, asymmetric leaves enhancer3 (ae3), which demonstrated pleiotropic plant phenotypes, including a defective adaxial identity in some leaves. The ae3 as2 double mutant displayed severely abaxialized leaves, which were accompanied by elevated levels of leaf abaxial promoting genes FILAMENTOUS FLOWER, YABBY3, KANADI1 (KAN1), and KAN2 and a reduced level of the adaxial promoting gene REVOLUTA. We identified AE3, which encodes a putative 26S proteasome subunit RPN8a. Furthermore, double mutant combinations of as2 with other 26S subunit mutations, including rpt2a, rpt4a, rpt5a, rpn1a, rpn9a, pad1, and pbe1, all displayed comparable phenotypes with those of ae3 as2, albeit with varying phenotypic severity. Since these mutated genes encode subunits that are located in different parts of the 26S proteasome, it is possible that the proteolytic function of the 26S holoenzyme is involved in leaf polarity formation. Together, our findings reveal that posttranslational regulation is essential in proper leaf patterning.

中文翻译：

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拟南芥26S蛋白酶体的蛋白水解功能是确定叶片近轴身份所必需的。

极性形成是叶片形态发生的中心，已经鉴定并广泛表征了在左右轴极性建立中起作用的几个关键基因。我们先前曾报道过拟南芥ASYMMERTIC LEAVES1（AS1）和AS2在促进叶片近轴命运方面很重要。我们获得了as2增强子突变体，不对称叶片增强子3（ae3），其表现出多效性植物表型，包括在某些叶片中存在缺陷的近轴同一性。ae3 as2双重突变体显示了严重的背面化叶片，并伴有水平升高的叶片背面促进基因FILAMENTOUS FLOWER，YABBY3，KANADI1（KAN1）和KAN2，以及水平降低的正面促进基因REVOLUTA。我们确定了AE3，它编码一个假定的26S蛋白酶体亚基RPN8a。此外，as2的双重突变组合与其他26S亚基突变，包括rpt2a，rpt4a，rpt5a，rpn1a，rpn9a，pad1和pbe1，尽管表型严重程度不同，但它们都表现出与ae3 as2相似的表型。由于这些突变的基因编码位于26S蛋白酶体不同部分的亚基，因此26S全酶的蛋白水解功能可能与叶片极性形成有关。总之，我们的发现表明，翻译后调控对于正确的叶片模式至关重要。26S全酶的蛋白水解功能可能与叶片极性形成有关。总之，我们的发现表明，翻译后调控对于正确的叶片模式至关重要。26S全酶的蛋白水解功能可能与叶片极性形成有关。总之，我们的发现表明，翻译后调控对于正确的叶片模式至关重要。