State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China.
State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Mol Plant. 2023 Jun 5;16(6):999-1015. doi: 10.1016/j.molp.2023.04.006. Epub 2023 Apr 12.
The orderly deposition of secondary cell wall (SCW) in plants is implicated in various biological programs and is precisely controlled. Although many positive and negative regulators of SCW have been documented, the molecular mechanisms underlying SCW formation coordinated with distinct cellular physiological processes during plant adaptive growth remain largely unclear. Here, we report the identification of Cellulose Synthase co-expressed Kinase1 (CSK1), which encodes a receptor-like cytoplasmic kinase, as a negative regulator of SCW formation and its signaling cascade in rice. Transcriptome deep sequencing of developing internodes and genome-wide co-expression assays revealed that CSK1 is co-expressed with cellulose synthase genes and is responsive to various stress stimuli. The increased SCW thickness and vigorous vessel transport in csk1 indicate that CSK1 functions as a negative regulator of SCW biosynthesis. Through observation of green fluorescent protein-tagged CSK1 in rice protoplasts and stable transgenic plants, we found that CSK1 is localized in the nucleus and cytoplasm adjacent to the plasma membrane. Biochemical and molecular assays demonstrated that CSK1 phosphorylates VASCULAR-RELATED NAC-DOMAIN 6 (VND6), a master SCW-associated transcription factor, in the nucleus, which reduces the transcription of a suite of SCW-related genes, thereby attenuating SCW accumulation. Consistently, genetic analyses show that CSK1 functions upstream of VND6 in regulating SCW formation. Interestingly, our physiological analyses revealed that CSK1 and VND6 are involved in abscisic acid-mediated regulation of cell growth and SCW deposition. Taken together, these results indicate that the CSK1-VND6 module is an important component of the SCW biosynthesis machinery, which coordinates SCW accumulation and adaptive growth in rice. Our study not only identifies a new regulator of SCW biosynthesis but also reveals a fine-tuned mechanism for precise control of SCW deposition, offering tools for rationally tailoring agronomic traits.
植物中次生细胞壁（SCW）的有序沉积与各种生物程序有关，并受到精确控制。虽然已经记录了许多 SCW 的正调控因子和负调控因子，但在植物适应生长过程中，与不同细胞生理过程相协调的 SCW 形成的分子机制在很大程度上仍不清楚。在这里，我们报道了纤维素合酶共表达激酶 1（CSK1）的鉴定，CSK1 编码一种受体样细胞质激酶，是水稻 SCW 形成的负调控因子及其信号级联。发育节间的转录组深度测序和全基因组共表达分析表明，CSK1 与纤维素合酶基因共表达，并对各种胁迫刺激有反应。csk1 中 SCW 厚度增加和有力的脉管运输表明 CSK1 作为 SCW 生物合成的负调控因子发挥作用。通过观察水稻原生质体和稳定转化植物中的绿色荧光蛋白标记的 CSK1，我们发现 CSK1 定位于细胞核和靠近质膜的细胞质中。生化和分子分析表明，CSK1 在核内磷酸化血管相关 NAC 结构域 6（VND6），这是一个主要的 SCW 相关转录因子，从而减少了一系列 SCW 相关基因的转录，从而减弱了 SCW 的积累。一致地，遗传分析表明 CSK1 在调节 SCW 形成中位于 VND6 的上游。有趣的是，我们的生理分析表明，CSK1 和 VND6 参与了脱落酸介导的细胞生长和 SCW 沉积的调节。总之，这些结果表明 CSK1-VND6 模块是 SCW 生物合成机制的重要组成部分，它协调了水稻中 SCW 的积累和适应性生长。我们的研究不仅鉴定了 SCW 生物合成的新调节剂，还揭示了精确控制 SCW 沉积的精细机制，为合理定制农艺性状提供了工具。
