A putative poplar PP2C-encoding gene negatively regulates drought and abscisic acid responses in transgenic Arabidopsis thaliana

Here we link for the first time a poplar gene with putative function in ABA signaling to the regulation of drought responses, providing a target for drought tolerance improvement in poplars.Populus species are valued for their fast growth and are cultivated widely. Many of the commonly used species and hybrids are, however, regarded as drought sensitive, which poses a problem for large-scale cultivation particularly in light of climate change-induced drought spells in areas of poplar growth. While many hundreds of drought-induced genes have been identified in Populus species, very little is known about the genes and the signaling process that leads to a drought response in these species. Based on sequence similarity, the poplar G059200 gene is a potential ortholog of AtPP2CA, an inhibitor of drought and abscisic acid (ABA) responses in Arabidopsis thaliana. To test if G059200 has a similar function, we generated transgenic A. thaliana plants overexpressing this gene. These transgenic lines exhibited reduced responses to exogenous ABA and reduced tolerance to osmotic stress. Finally, drought tolerance of plants was also significantly reduced. Taken together, these data provide evidences that G059200 acts as a negative regulator of ABA responses. The ability to negatively regulate drought stress responses suggests that G059200 may be targeted for drought tolerance breeding, for example, by identification of individuals harboring natural or induced loss-of-function alleles, or by RNA interference technology, to generate poplar plants with reduced activity of G059200.

在此，我们首次将一个在脱落酸（ABA）信号传导中具有假定功能的杨树基因与干旱响应的调控联系起来，为杨树耐旱性的提高提供了一个靶点。杨树因其生长迅速而受到重视，并被广泛种植。然而，许多常用的品种和杂交种被认为对干旱敏感，这给大规模种植带来了问题，特别是考虑到气候变化导致杨树生长地区出现干旱期。虽然在杨树中已经鉴定出数百个受干旱诱导的基因，但对于导致这些树种产生干旱响应的基因和信号传导过程知之甚少。基于序列相似性，杨树的G059200基因是拟南芥AtPP2CA的一个潜在直系同源基因，AtPP2CA是拟南芥中干旱和脱落酸（ABA）响应的抑制剂。为了测试G059200是否具有类似功能，我们培育了过量表达该基因的转基因拟南芥植株。这些转基因株系对外源ABA的响应降低，对渗透胁迫的耐受性降低。最后，植株的耐旱性也显著降低。综上所述，这些数据提供了证据表明G059200作为ABA响应的负调控因子起作用。负调控干旱胁迫响应的能力表明，G059200可能成为耐旱育种的目标，例如，通过鉴定携带自然或诱导的功能缺失等位基因的个体，或者通过RNA干扰技术，来培育G059200活性降低的杨树植株。