Abstract：
PXY (Phloem intercalated with xylem) is a receptor kinase required for directional cell division during the development of plant vascular tissue. Drought stress usually affects plant stem cell division and differentiation thereby limiting plant growth. However, the role of PXY in cambial activities of woody plants under drought stress is unclear. In this study, we analyzed the biological functions of two PXY genes (PagPXYa and PagPXYb) in poplar growth and development and in response to drought stress in a hybrid poplar (Populus alba × P. glandulosa, \'84K\'). Expression analysis indicated that PagPXYs, similar to their orthologs PtrPXYs in Populus trichocarpa, are mainly expressed in the stem vascular system, and related to drought. Interestingly, overexpression of PagPXYa and PagPXYb in poplar did not have a significant impact on the growth status of transgenic plants under normal condition. However, when treated with 8 % PEG6000 or 100 mM H2O2, PagPXYa and PagPXYb overexpressing lines consistently exhibited more cambium cell layers, fewer xylem cell layers, and enhanced drought tolerance compared to the non-transgenic control \'84K\'. In addition, PagPXYs can alleviate the damage caused by H2O2 to the cambium under drought stress, thereby maintaining the cambial division activity of poplar under drought stress, indicating that PagPXYs play an important role in plant resistance to drought stress. This study provides a new insight for further research on the balance of growth and drought tolerance in forest trees.
摘要：
PXY（插入木质部的韧皮部）是植物维管组织发育过程中定向细胞分裂所需的受体激酶。干旱胁迫通常影响植物干细胞的分裂和分化,从而限制植物生长。然而,PXY在干旱胁迫下木本植物形成层活动中的作用尚不清楚。在这项研究中,我们分析了两个PXY基因（PagPXYa和PagPXYb）在杨树生长发育以及对干旱胁迫的响应中的生物学功能。glandulosa\'84K\'。表达分析表明，PagPXYs，与毛果杨中的直系同源物PtrPXY相似，主要在茎血管系统中表达，与干旱有关。有趣的是,PagPXYa和PagPXYb在杨树中的过表达对正常条件下转基因植株的生长状况没有显著影响。然而,当用8％PEG6000或100mMH2O2处理时，PagPXYa和PagPXYb过表达的细胞系始终表现出更多的形成层细胞层，木质部细胞层较少，与非转基因对照“84K”相比，耐旱性增强。此外,PagPXYs可以缓解干旱胁迫下H2O2对形成层的伤害，从而在干旱胁迫下保持杨树的形成层分裂活动，说明PagPXYs在植物抗干旱胁迫中起重要作用。本研究为进一步研究林木生长与耐旱性的平衡提供了新的思路。
