Chongqing Key Laboratory of Plant Resource Conservation and Germplasm Innovation, Integrative Science Center of Germplasm Creation in Western China (Chongqing) Science City, Key Laboratory of Eco-Environments of Three Gorges Reservoir Region, Ministry of Education, Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing 400715, China.
Tree Physiol. 2024 Feb 11;44(3). doi: 10.1093/treephys/tpad153.
The critical role of auxin on secondary vascular development in woody plants has been demonstrated. The concentration gradient of endogenous indole-3-acetic acid and the cellular and molecular pathways contributing to the auxin-directed vascular organization and wood growth have been uncovered in recent decades. However, our understanding of the roles and regulations of auxin influx in wood formation in trees remains limited. Here, we reported that a microRNA, miR7833, participates in the negative regulation of stem cambial cell division and secondary xylem development in Populus tomentosa. The miR7833 is mainly expressed in the vascular cambium during stem radical growth and specifically targets and represses two AUX/LAX family auxin influx carriers, AUX5 and AUX6, in poplar. We further revealed that poplar AUX6, the most abundant miR7833 target in the stem, is preferentially enriched in the developing xylem and is a positive regulator for cell division and differentiation events during wood formation. Moreover, inhibition of auxin influx carriers by 1-naphthoxyacetic acids abolished the regulatory effects of miR7833 and AUX6 on secondary xylem formation in poplar. Our results revealed the essential roles of the miR7833-AUX6 module in regulating cellular events in secondary xylem development and demonstrated an auxin influx-dependent mechanism for wood formation in poplar.
生长素在木本植物次生维管发育中的关键作用已经得到证实。在过去几十年中，已经揭示了内源性吲哚-3-乙酸的浓度梯度以及有助于生长素指导的维管束组织和木材生长的细胞和分子途径。然而，我们对生长素流入在树木形成木材中的作用和调节的理解仍然有限。在这里，我们报道了 microRNA miR7833 参与毛白杨茎形成层细胞分裂和次生木质部发育的负调控。miR7833 在茎根生长期间主要在维管束形成层中表达，并且特异性靶向和抑制杨树中的两个 AUX/LAX 家族生长素流入载体 AUX5 和 AUX6。我们进一步揭示了杨树 AUX6 是茎中 miR7833 的最丰富靶标，优先富集在发育中的木质部中，并且是形成木材过程中细胞分裂和分化事件的正调节剂。此外，1-萘氧基乙酸抑制生长素流入载体，消除了 miR7833 和 AUX6 对毛白杨次生木质部形成的调节作用。我们的结果揭示了 miR7833-AUX6 模块在调节次生木质部发育中的细胞事件中的重要作用，并证明了生长素流入依赖的机制在杨树形成木材中的作用。
