Verslues Paul E, Bray Elizabeth A
Department of Botany and Plant Sciences and Center for Plant Cell Biology, University of California, Riverside, CA 92521, USA.
J Exp Bot. 2006;57(1):201-12. doi: 10.1093/jxb/erj026. Epub 2005 Dec 9.
The mechanisms by which plants respond to reduced water availability (low water potential) include both ABA-dependent and ABA-independent processes. Pro accumulation and osmotic adjustment are two important traits for which the mechanisms of regulation by low water potential, and the involvement of ABA, is not well understood. The ABA-deficient mutant, aba2-1, was used to investigate the regulatory role of ABA in low water potential-induced Pro accumulation and osmotic adjustment in seedlings of Arabidopsis thaliana. Low water potential-induced Pro accumulation required wild-type levels of ABA, as well as a change in ABA sensitivity or ABA-independent events. Osmotic adjustment, in contrast, occurred independently of ABA accumulation in aba2-1. Quantification of low water potential-induced ABA and Pro accumulation in five ABA-insensitive mutants, abi1-1, abi2-1, abi3, abi4, and abi5, revealed that abi4 had increased Pro accumulation at low water potential, but a reduced response to exogenous ABA. Both of these responses were modified by sucrose treatment, indicating that ABI4 has a role in connecting ABA and sugar in regulating Pro accumulation. Of the other abi mutants, only abi1 had reduced Pro accumulation in response to low water potential and ABA application. It was also observed that abi1-1 and abi2-1 had increased ABA accumulation. The involvement of these loci in feedback regulation of ABA accumulation may occur through an effect on ABA catabolism or conjugation. These data provide new information on the function of ABA in seedlings exposed to low water potential and define new roles for three of the well-studied abi loci.
植物对水分可利用性降低（低水势）做出响应的机制包括依赖脱落酸（ABA）和不依赖ABA的过程。脯氨酸（Pro）积累和渗透调节是两个重要特性，低水势对其调控机制以及ABA的参与情况尚不清楚。利用ABA缺陷型突变体aba2-1来研究ABA在拟南芥幼苗低水势诱导的Pro积累和渗透调节中的调控作用。低水势诱导的Pro积累需要野生型水平的ABA，以及ABA敏感性的变化或不依赖ABA的事件。相比之下，aba2-1中的渗透调节独立于ABA积累而发生。对五个ABA不敏感突变体abi1-1、abi2-1、abi3、abi4和abi5中低水势诱导的ABA和Pro积累进行定量分析，结果表明abi4在低水势下Pro积累增加，但对外源ABA的响应降低。这两种响应都因蔗糖处理而改变，表明ABI4在调节Pro积累过程中连接ABA和糖方面发挥作用。在其他abi突变体中，只有abi1对低水势和ABA处理的响应中Pro积累减少。还观察到abi1-1和abi2-1的ABA积累增加。这些位点参与ABA积累的反馈调节可能是通过对ABA分解代谢或缀合作用的影响来实现的。这些数据提供了关于ABA在低水势条件下幼苗中功能的新信息，并确定了三个研究充分的abi位点的新作用。
