Abstract

Trichomes are specialized epidermal appendages that serve as excellent models to study cell morphogenesis. Although the molecular mechanism underlying trichome morphogenesis in Arabidopsis has been well characterized, most of the regulators essential for multicellular trichome morphology remain unknown in tomato. In this study, we determined that the recessive hairless-2 (hl-2) mutation in tomato causes severe distortion of all trichome types, along with increased stem fragility. Using map-based cloning, we found that the hl-2 phenotype was associated with a 100 bp insertion in the coding region of Nck-associated protein 1, a component of the SCAR/WAVE complex. Direct protein-protein interaction was detected between Hl-2 and Hl (SRA1, specifically Rac1-associated protein) using yeast two-hybrid and co-immunoprecipitation assays, suggesting that these proteins may work together during trichome formation. In addition, knock-down of a HD-Zip IV transcription factor, HDZIPIV8, distorted trichomes similar to the hl-2 mutant. HDZIPIV8 regulates the expression of Hl-2 by binding to the L1-box in the Hl-2 promoter region, and is involved in organizing actin filaments. The brittleness of hl-2 stems was found to result from decreased cellulose content. Taken together, these findings suggest that the Hl-2 gene plays an important role in controlling multicellular trichome morphogenesis and mechanical properties of stems in tomato plants.

中文翻译：

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HD-Zip IV转录因子SlHDZIV8通过调节Hairless-2的表达来控制多细胞毛状体形态。

摘要

毛滴虫是专门的表皮附件，可作为研究细胞形态发生的优秀模型。尽管拟南芥中毛状体形态发生的分子机制已得到很好的表征，但番茄中对多细胞毛状体形态必不可少的大多数调节剂仍然未知。在这项研究中，我们确定番茄中的隐性无毛2（hl-2）突变会引起所有毛状体类型的严重畸变，并增加茎的脆性。使用基于图的克隆，我们发现hl-2该表型与Nck相关蛋白1（SCAR / WAVE复合物的组成部分）的编码区插入100 bp有关。使用酵母双杂交和共免疫沉淀测定法检测到H1-2和H1（SRA1，特别是Rac1相关蛋白）之间存在直接的蛋白质-蛋白质相互作用，表明这些蛋白质可能在毛状体形成过程中一起起作用。另外，敲低HD-Zip IV转录因子HDZIPIV8使类似于hl-2突变体的毛状体扭曲。HDZIPIV8调节的表达的H1-2通过结合到在该L1-箱的III-2启动子区，并参与组织肌动蛋白丝。hl-2的脆性发现茎干是由于纤维素含量降低所致。综上所述，这些发现表明H1-2基因在控制番茄植物的多细胞毛状体形态发生和茎的机械特性中起重要作用。