Experimental Center of Forestry in North China, Chinese Academy of Forestry, Beijing 100023, PR China.
State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, PR China.
J Plant Physiol. 2019 Feb;233:58-72. doi: 10.1016/j.jplph.2018.12.007. Epub 2018 Dec 19.
Proline-rich protein (PRP) is a plant cell wall associated protein. Its distinct patterns of regulation and localization studied in a number of plants indicate that it may play important roles in growth and development. However, the mechanism of how these genes control secondary cell wall development in tree species is largely unknown. Here, we report that a Populus deltoides (Marsh.) proline-rich protein gene PdPRP was preferentially expressed in immature/mature phloem and immature xylem in P. deltoides. PdPRP overexpression increased poplar plant height and diameter as well as the radial width of the phloem and xylem regions, facilitated secondary wall deposition, and induced expression of genes related to microfibril angle (MFA) and secondary wall biosynthesis. Downregulation of PdPRP retarded poplar growth, decreased the radial width of the secondary phloem and secondary xylem regions, reduced secondary wall thickening in fibers and vessels, and decreased the expression of genes related to MFA and secondary wall biosynthesis. These results suggest that PdPRP might positively regulate secondary cell wall formation by promoting secondary wall thickening and expansion in poplar. PdPRP-overexpressing poplar had a lower MFA, indicating that PdPRP may be useful for improving wood stiffness and properties in plants. Together, our results demonstrate that PdPRP is a proline-rich protein associated with cell wall development, playing a critical role in regulating secondary cell wall formation in poplar.
富含脯氨酸的蛋白（PRP）是一种与植物细胞壁相关的蛋白。在许多植物中对其调控和定位的独特模式的研究表明，它可能在生长和发育中发挥重要作用。然而，这些基因如何控制树种次生细胞壁发育的机制在很大程度上尚不清楚。在这里，我们报道了一个杨树富含脯氨酸的蛋白基因 PdPRP 在杨树的未成熟/成熟韧皮部和未成熟木质部中优先表达。PdPRP 的过表达增加了杨树的株高和直径，以及韧皮部和木质部区域的径向宽度，促进了次生壁的沉积，并诱导了与微纤丝角（MFA）和次生壁生物合成相关的基因的表达。PdPRP 的下调减缓了杨树的生长，降低了次生韧皮部和次生木质部区域的径向宽度，减少了纤维和导管中次生壁的增厚，并降低了与 MFA 和次生壁生物合成相关的基因的表达。这些结果表明，PdPRP 可能通过促进杨树次生壁的增厚和扩张来正向调节次生细胞壁的形成。PdPRP 过表达的杨树具有较低的 MFA，表明 PdPRP 可能有助于提高植物的木材硬度和性能。总之，我们的结果表明，PdPRP 是一种与细胞壁发育相关的富含脯氨酸的蛋白，在调节杨树次生细胞壁形成中起着关键作用。
