UCA, INRA, PIAF, 63000, Clermont-Ferrand, France.
UCA, EA 4678 CIDAM, 63000, Clermont-Ferrand, France.
Physiol Plant. 2018 Aug;163(4):502-515. doi: 10.1111/ppl.12702. Epub 2018 Apr 23.
While the xylem hydraulic properties, such as vulnerability to cavitation (VC), are of paramount importance in drought resistance, their genetic determinants remain unexplored. There is evidence that pectins and their methylation pattern are involved, but the detail of their involvement and the corresponding genes need to be clarified. We analyzed the hydraulic properties of the 35S::PME1 transgenic aspen that ectopically under- or over-express a xylem-abundant pectin methyl esterase, PtxtPME1. We also produced and analyzed 4CL1::PGII transgenic poplars expressing a fungal polygalacturonase, AnPGII, under the control of the Ptxa4CL1 promoter that is active in the developing xylem after xylem cell expansion. Both the 35S::PME1 under- and over-expressing aspen lines developed xylem with lower-specific hydraulic conductivity and lower VC, while the 4CL1::PGII plants developed xylem with a higher VC. These xylem hydraulic changes were associated with modifications in xylem structure or in intervessel pit structure that can result in changes in mechanical behavior of the pit membrane. This study shows that homogalacturonans and their methylation pattern influence xylem hydraulic properties, through its effect on xylem cell expansion and on intervessel pit properties and it show a role for PtxtPME1 in the xylem hydraulic properties.
木质部水力特性（如对空化的脆弱性（VC））对耐旱性至关重要，但它们的遗传决定因素仍未得到探索。有证据表明果胶及其甲基化模式与之相关，但它们的具体参与程度和相应的基因仍需阐明。我们分析了过表达或低表达木质部丰富果胶甲酯酶 PtxtPME1 的 35S::PME1 转基因白杨的水力特性。我们还生产并分析了 4CL1::PGII 转基因杨树，其在木质部细胞扩张后活跃的 Ptxa4CL1 启动子的控制下表达真菌多聚半乳糖醛酸酶 AnPGII。过表达和低表达 35S::PME1 的白杨系木质部的比导水率和 VC 均较低，而 4CL1::PGII 植株的木质部 VC 较高。这些木质部水力变化与木质部结构或纹孔间纹孔结构的改变有关，这可能导致纹孔膜的机械行为发生变化。本研究表明，同型半乳糖醛酸聚糖及其甲基化模式通过影响木质部细胞扩张和纹孔间纹孔特性来影响木质部水力特性，并显示 PtxtPME1 在木质部水力特性中的作用。
