• Since the roots are the very organ where plants first sense and respond drought stress, it is of great importance to better understand root responses to drought. Yet the underlying molecular mechanisms governing root responses to drought stress have been poorly understood.
• Here, we identified and functionally characterized a CCCH type transcription factor, PuC3H35, and its targets, anthocyanin reductase (PuANR) and early Arabidopsis aluminum induced1 (PuEARLI1), which are involved in mediating proanthocyanidin (PA) and lignin biosynthesis in response to drought stress in Populus ussuriensis root.
• PuC3H35 was root-specifically induced upon drought stress. Overexpressing PuC3H35 promoted PA and lignin biosynthesis and vascular tissue development, resulting in enhanced tolerance to drought stress by the means of anti-oxidation and mechanical supporting. We further demonstrated that PuC3H35 directly bound to the promoters of PuANR and PuEARLI1 and overexpressing PuANR or PuEARLI1 increased root PA or lignin levels, respectively, under drought stress.
• Taken together, these results revealed a novel regulatory pathway for drought tolerance, in which PuC3H35 mediated PA and lignin biosynthesis by collaboratively regulating ‘PuC3H35-PuANR-PA’ and ‘PuC3H35-PuEARLI1-PuCCRs-lignin’ modules in poplar roots.

中文翻译：

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PuC3H35通过增强乌苏里杨根中木质素和原花青素的生物合成来赋予耐旱性

• 由于根是植物首先感知和响应干旱胁迫的器官，因此更好地了解根对干旱的响应非常重要。然而，人们对根系对干旱胁迫响应的潜在分子机制知之甚少。
• 在这里，我们鉴定并在功能上表征了 CCCH 型转录因子 PuC3H35 及其靶标花青素还原酶 ( PuANR ) 和早期拟南芥铝诱导 1 ( PuEARLI1 )，它们参与介导原花青素 (PA) 和木质素生物合成以响应干旱胁迫在乌苏里杨根中。
• PuC3H35在干旱胁迫下被根特异性诱导。过表达PuC3H35促进了PA和木质素的生物合成和维管组织的发育，通过抗氧化和机械支持增强了对干旱胁迫的耐受性。我们进一步证明了在干旱胁迫下，PuC3H35 直接与PuANR和PuEARLI1的启动子结合，过表达PuANR或PuEARLI1 分别增加了根 PA 或木质素水平。
• 总之，这些结果揭示了一种新的耐旱性调节途径，其中 PuC3H35 通过协同调节杨树根中的“PuC3H35-PuANR-PA”和“PuC3H35-PuEARLI1-PuCCRs-木质素”模块来介导 PA 和木质素的生物合成。