Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, PR China.
Key Laboratory of Cotton and Rape in Lower Reaches of Yangtze River, Ministry of Agriculture, Nanjing, PR China.
Plant Cell Environ. 2019 Jul;42(7):2120-2132. doi: 10.1111/pce.13548. Epub 2019 Apr 16.
Basal branching in grasses, or tillering, is an important trait determining both form and function of crops. Although similarities exist between eudicot and grass branching programs, one notable difference is that the tiller buds of grasses are covered by the subtending leaf, whereas eudicot buds are typically unconstrained. The current study shows that contact with the leaf sheath represses sorghum bud growth by providing a mechanical signal that cues the bud to refrain from rapid growth. Leaf removal resulted in massive reprogramming of the bud transcriptome that included signatures of epigenetic modifications and also implicated several hormones in the response. Bud abscisic acid transiently increased, then decreased following leaf removal relative to controls, and abscisic acid was necessary to repress bud growth in the presence of the leaf. Jasmonic acid (JA) levels and signalling increased in buds following leaf removal. Remarkably, application of JA to buds in situ promoted growth. The repression of bud growth by leaf contact shares characteristics of thigmomorphogenic responses in other systems, including the involvement of JA, though the JA effect is opposite. The repression of bud growth by leaf contact may represent a mechanism to time tillering to an appropriate developmental stage of the plant.
禾本科植物的基部分枝，即分蘖，是决定作物形态和功能的重要特征。尽管真双子叶植物和禾本科植物的分枝程序有一些相似之处，但一个显著的区别是禾本科植物的分蘖芽被下一叶鞘覆盖，而真双子叶植物的芽通常不受限制。本研究表明，与叶鞘的接触通过提供一个机械信号来抑制高粱芽的生长，该信号提示芽停止快速生长，从而抑制芽的生长。叶鞘去除导致芽转录组发生大规模重编程，包括表观遗传修饰的特征，并暗示了几种激素在该反应中的作用。与对照相比，叶鞘去除后，芽内脱落酸的含量短暂增加，然后减少，而在有叶鞘的情况下，脱落酸是抑制芽生长所必需的。茉莉酸（JA）水平和信号在叶鞘去除后在芽中增加。值得注意的是，JA 在原位应用于芽中促进了芽的生长。叶鞘接触对芽生长的抑制与其他系统中的向触性反应具有共同特征，包括茉莉酸的参与，尽管茉莉酸的作用是相反的。叶鞘接触对芽生长的抑制可能代表了一种使分蘖发生在植物适当发育阶段的机制。
