The morphology of bulliform cells located on the upper epidermis of leaves is one of the most important cell structures affecting leaf shape. Although many mechanisms regulating the development of bulliform cells have been reported, the fine regulatory mechanisms governing this process have rarely been described. To identify novel components regulating rice leaf morphology, a mutant showing a constitutively rolling phenotype from the seedling stage to flowering, known as crm1‐D, was selected for further analysis. Anatomical analyses in crm1‐D were attributable to the size reduction of bulliform cells. The crm1‐D was controlled by a single dominant nuclear gene. Map‐based cloning revealed that Roc8, an HD zipper class IV family member, was responsible for the crm1‐D phenotype. Notably, the 50‐bp sequence in the 3′‐untranslated region (3′‐UTR) of the Roc8 gene represses Roc8 at the translational level. Moreover, the roc8 knockdown lines notably increased the size of bulliform cells. A series of assays revealed that Roc8 negatively regulates the size of bulliform cells. Unexpectedly, Roc8 was also observed to positively mediate lignin biosynthesis without incurring a production penalty. The above results show that Roc8 may have a practical application in cultivating materials with high photosynthetic efficiency and low lignin content.

中文翻译：

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HD-ZIP IV基因Roc8调节大米状细胞的大小和木质素含量。

位于叶片上表皮的大疱状细胞的形态是影响叶片形状的最重要的细胞结构之一。尽管已报道了许多调控大疱状细胞发育的机制，但很少描述控制该过程的精细调控机制。为了鉴定调节稻叶形态的新成分，选择了一个显示从苗期到开花的组成型滚动表型的突变体crm1-D进行进一步分析。crm1-D的解剖学分析归因于大疱状细胞的大小减小。该CRM1-d是由一对显性核基因控制。基于地图的克隆显示，Roc8，HD拉链IV级家庭成员负责crm1-D表型。值得注意的是，Roc8基因3'-非翻译区（3'-UTR）中的50 bp序列在翻译水平上抑制了Roc8。而且，roc8敲低系显着增加了疱状细胞的大小。一系列测定表明，Roc8负调控着大疱状细胞的大小。出乎意料的是，还观察到Roc8积极介导木质素的生物合成而不会产生生产损失。以上结果表明，Roc8在光合作用效率高，木质素含量低的材料上具有实际应用价值。