A HD-ZIP III gene, PtrHB4, is required for interfascicular cambium development in Populus

Corresponding author: Laigeng Li

Wood production is dependent on the activity of the vascular cambium (维管形成层), which develops from the fascicular and interfascicular cambia (束中、束间形成层). However, little is known about the mechanisms controlling how the vascular cambium is developed in woody species. Here, we show that PtrHB4, belonging to the Populus HD-ZIP III family, plays a critical role in the process of vascular cambium development. PtrHB4 was specifically expressed in shoot tip (茎尖) and stem vascular tissue at an early developmental stage. Repression of PtrHB4 caused defects in the development of the secondary vascular system due to failures in interfascicular cambium formation. By contrast, overexpression of PtrHB4 induced cambium activity and xylem differentiation during secondary vascular development. Transcriptional analysis of PtrHB4 repressed plants indicated that auxin response and cell proliferation (细胞增殖) were affected in the formation of the interfascicular cambium. Taken together, these results suggest that PtrHB4 is required for interfascicular cambium formation to develop the vascular cambium in woody species.

木材形成依赖于维管形成层的活性，而维管形成层是从束中、束间形成层发育而来。然而，对于木本植物中控制维管形成层的机制还不清楚。本文的试验表明杨树的HD-ZIP III家族PtrHB4基因在维管形成层发育过程中起到重要的作用。PtrHB4基因在茎尖和茎的维管组织中特异表达。抑制PtrHB4基因会引起由于束间形成层形成失败导致的次生维管系统的发育缺陷。相反，过表达PtrHB4基因会诱导次生维管发育过程中的形成层活性和木质部分化。PtrHB4基因抑制植株的转录分析显示束间形成层形成中的生长素响应和细胞增殖受到影响。综上，这些结果表明PtrHB4基因在木本植物束间形成层形成以发育成维管形成层中起重要作用。

个人简介：1982年，中南林学院，学士；1985年，中南林学院，硕士；1997年，Michigan Technological University，博士。

研究方向： 1. 植物细胞壁生物合成的分子生物学与基因工程研究； 2. 木质部细胞分化的分子调控机理研究； 3. 木质纤维生物质合成的功能基因组学研究； 4. 有效利用木质纤维生物质能源的技术研究。

doi: 10.1111/pbi.12830