Plant cell growth involves a complex interplay among cell-wall expansion, biosynthesis, and, in specific tissues, secondary cell wall (SCW) deposition, yet the coordination of these processes remains elusive. Cotton fiber cells are developmentally synchronous, highly elongated, and contain nearly pure cellulose when mature. Here, we report that the transcription factor GhTCP4 plays an important role in balancing cotton fiber cell elongation and wall synthesis. During fiber development the expression of miR319 declines while GhTCP4 transcript levels increase, with high levels of the latter promoting SCW deposition. GhTCP4 interacts with a homeobox-containing factor, GhHOX3, and repressing its transcriptional activity. GhTCP4 and GhHOX3 function antagonistically to regulate cell elongation, thereby establishing temporal control of fiber cell transition to the SCW stage. We found that overexpression of GhTCP4A upregulated and accelerated activation of the SCW biosynthetic pathway in fiber cells, as revealed by transcriptome and promoter activity analyses, resulting in shorter fibers with varied lengths and thicker walls. In contrast, GhTCP4 downregulation led to slightly longer fibers and thinner cell walls. The GhHOX3–GhTCP4 complex may represent a general mechanism of cellular development in plants since both are conserved factors in many species, thus providing us a potential molecular tool for the design of fiber traits.

植物细胞的生长涉及细胞壁扩张，生物合成以及特定组织中的次生细胞壁（SCW）沉积之间的复杂相互作用，但是这些过程的协调仍然难以捉摸。棉纤维细胞在发育上是同步的，高度伸长，成熟时几乎含有纯纤维素。在这里，我们报道转录因子GhTCP4在平衡棉纤维细胞伸长和壁合成中起重要作用。在纤维发育过程中，miR319的表达下降，而GhTCP4转录水平增加，后者的高水平促进SCW沉积。GhTCP4与包含同源异型框的因子GhHOX3相互作用，并抑制其转录活性。GhTCP4和GhHOX3具有拮抗作用，可调节细胞伸长，从而建立对光纤细胞过渡到SCW阶段的时间控制。我们发现 如转录组和启动子活性分析所揭示的，GhTCP4A上调并加速了纤维细胞中SCW生物合成途径的激活，从而导致了较短的纤维具有不同的长度和较厚的壁。相反，GhTCP4下调导致纤维稍长，细胞壁更薄。GhHOX3-GhTCP4复合体可能代表植物细胞发育的一般机制，因为两者都是许多物种中的保守因子，因此为我们提供了设计纤维性状的潜在分子工具。