Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Science, Kunming, 650201, China.
Plant Germplasm and Genomics Center, the Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China.
Protoplasma. 2021 Sep;258(5):925-934. doi: 10.1007/s00709-021-01609-1. Epub 2021 Mar 24.
Turnip is a member of the Brassica rapa species and is characterized by a swollen taproot that develops from the hypocotyl and part of the root. Gibberellins (GAs) are plant growth regulators involved in promoting cell elongation and play important roles in many aspects of plant growth and development. Interestingly, exogenous application of GA was found to significantly inhibit taproot formation in turnip. Moreover, endogenous GA contents decreased during the early developmental stages of taproot formation, suggesting that GA plays a negative role in taproot formation. We examined the anatomical structure of the taproot and found that lignification of the xylem cell wall was enhanced after treatment with GA. Yeast two-hybrid assays suggested the occurrence of protein interactions between DELLAs and NACs in turnip. We also found that the expression of NAC-targeted genes involved in lignification of the secondary cell wall was significantly upregulated upon GA treatment. Taken together, these results supported the hypothesis that GA induced DELLA proteins degradation to release NAC proteins and induced xylem lignification, therefore inhibiting taproot formation, providing new insight into the molecular mechanism underlying turnip taproot formation.
萝卜是芸薹属的一员，其特征是从下胚轴和部分根部长出的膨大块根。赤霉素（GAs）是参与促进细胞伸长的植物生长调节剂，在植物生长和发育的许多方面发挥着重要作用。有趣的是，外源施用 GA 被发现可显著抑制萝卜块根的形成。此外，在块根形成的早期发育阶段，内源 GA 含量下降，表明 GA 在块根形成中发挥负调控作用。我们检查了块根的解剖结构，发现 GA 处理后木质部细胞壁的木质化增强。酵母双杂交实验表明，萝卜中 DELLAs 和 NACs 之间发生了蛋白相互作用。我们还发现，GA 处理后，参与次生细胞壁木质化的 NAC 靶基因的表达显著上调。综上所述，这些结果支持了 GA 诱导 DELLA 蛋白降解以释放 NAC 蛋白并诱导木质部木质化，从而抑制块根形成的假说，为萝卜块根形成的分子机制提供了新的见解。
