In response to variable environments, rice (Oryza sativa) roots have developed lignified and suberized diffusion barriers at the endodermis to permit selective nutrient uptake for optimal growth. Here, we demonstrate that endodermal suberization and non-localized lignification are redundantly regulated by four MYB transcription factors: OsMYB39a, OsMYB41, OsMYB92a, and OsMYB92b. These transcription factors function downstream of the OsMYB36a/b/c, CASPARIAN STRIP INTEGRITY FACTOR (OsCIF)–SCHENGEN3 (OsSGN3), and stress-inducible signaling pathways in rice. Knockout of all four MYB genes resulted in the complete absence of endodermal suberin lamellae (SL) and almost no lignin deposition between the Casparian strip and the cortex-facing lignified band at cell corners under all conditions examined. In contrast, endodermis-specific overexpression of any of these MYB genes was sufficient to induce strong endodermal suberization and non-localized lignification near the root tip. Furthermore, OsMYB92a-overexpressing lines showed an altered ionomic profile and enhanced salinity tolerance. Transcriptome analysis identified 152 downstream genes regulated by OsMYB39a/41/92a/92b, including the key SL formation gene OsCYP86A1 and other genes involved in endodermal lignification and suberization under normal and stress conditions. Our results provide important insights into the molecular mechanisms underlying suberization and non-localized lignification at the root endodermis and their physiological significance in ion homeostasis and acclimation to environmental stress.

中文翻译：

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4 种 MYB 转录因子调节水稻根内皮的 suberization 和非局部木质化


为了应对可变的环境，水稻 （Oryza sativa） 根在内胚层处发育出木质化和亚型扩散屏障，以允许选择性吸收养分以实现最佳生长。在这里，我们证明内胚层亚化和非局部木质化受四种 MYB 转录因子的冗余调节：OsMYB39a、OsMYB41、OsMYB92a 和 OsMYB92b。这些转录因子在水稻中 OsMYB36a/b/c、CASPARIAN 条带完整性因子 （OsCIF）-SCHENGEN3 （OsSGN3） 和胁迫诱导信号通路的下游发挥作用。敲除所有 4 个 MYB 基因导致内胚层木脂蛋白薄片 （SL） 完全缺失，并且在检查的所有条件下，Casparian 条带和细胞角面向皮层的木质化带之间几乎没有木质素沉积。相比之下，这些 MYB 基因中的任何一个的内皮特异性过表达都足以诱导根尖附近的强烈内胚层亚化和非局部木质化。此外，OsMYB92a 过表达细胞系显示出电离学特征改变和耐盐性增强。转录组分析鉴定出 152 个受 OsMYB39a/41/92a/92b 调控的下游基因，包括关键的 SL 形成基因 OsCYP86A1 和其他在正常和应激条件下参与内胚层木质化和下质化的基因。我们的结果为根内皮下沉化和非局部木质化的分子机制及其在离子稳态和适应环境胁迫中的生理意义提供了重要的见解。