Shanghai Key Lab of Bio-energy Crops, School of Life Sciences, Shanghai University, Shanghai, 200444, China.
National Key Laboratory of Plant Molecular Genetics and CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
Planta. 2018 May;247(5):1149-1161. doi: 10.1007/s00425-018-2851-8. Epub 2018 Jan 31.
PtrGH9A7, a poplar β-type endo-1,4-β-glucanase gene induced by auxin, promotes both plant growth and lateral root development by enhancing cell expansion. Endo-1,4-β-glucanase (EGase) family genes function in multiple aspects of plant growth and development. Our previous study found that PtrCel9A6, a poplar EGase gene of the β subfamily, is specifically expressed in xylem tissue and is involved in the cellulose biosynthesis required for secondary cell wall formation (Yu et al. in Mol Plant 6:1904-1917, 2013). To further explore the functions and regulatory mechanism of β-subfamily EGases, we cloned and characterized another poplar β-type EGase gene PtrGH9A7, a close homolog of PtrCel9A6. In contrast to PtrCel9A6, PtrGH9A7 is predominantly expressed in parenchyma tissues of the above-ground part; in roots, PtrGH9A7 expression is specifically restricted to lateral root primordia at all stages from initiation to emergence and is strongly induced by auxin application. Heterologous overexpression of PtrGH9A7 promotes plant growth by enhancing cell expansion, suggesting a conserved role for β-type EGases in 1,4-β-glucan chains remodeling, which is required for cell wall loosening. Moreover, the overexpression of PtrGH9A7 significantly increases lateral root number, which might result from improved lateral root primordium development due to enhanced cell expansion. Taken together, these results demonstrate that this β-type EGase induced by auxin signaling has a novel role in promoting lateral root formation as well as in enhancing plant growth.
PtrGH9A7，一种受生长素诱导的杨树β-型内切 1,4-β-葡聚糖酶基因，通过促进细胞扩张，同时促进植物生长和侧根发育。内切 1,4-β-葡聚糖酶（EGase）家族基因在植物生长和发育的多个方面发挥作用。我们之前的研究发现，杨树 EGase 基因β亚家族的 PtrCel9A6 特异性表达于木质部组织，参与次生细胞壁形成所需的纤维素生物合成（Yu 等人，Mol Plant 6:1904-1917, 2013）。为了进一步探索β-亚家族 EGases 的功能和调控机制，我们克隆并鉴定了另一个杨树β-型 EGase 基因 PtrGH9A7，它是 PtrCel9A6 的近同源基因。与 PtrCel9A6 不同，PtrGH9A7 主要在地上部分的薄壁组织中表达；在根中，PtrGH9A7 的表达特异性限制在从起始到出现的所有侧根原基阶段，并强烈被生长素处理诱导。PtrGH9A7 的异源过表达通过增强细胞扩张促进植物生长，表明β-型 EGases 在 1,4-β-葡聚糖链重塑中具有保守作用，这是细胞壁松弛所必需的。此外，PtrGH9A7 的过表达显著增加了侧根的数量，这可能是由于细胞扩张增强导致侧根原基发育改善所致。总之，这些结果表明，这种受生长素信号诱导的β-型 EGase 在促进侧根形成以及增强植物生长方面具有新的作用。
