Hwang Yong-sic, Bethke Paul C, Gubler Frank, Jones Russell L
Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102, USA.
Plant J. 2003 Jul;35(2):154-63. doi: 10.1046/j.1365-313x.2003.01789.x.
The putative H+/Cl- symporter cycloprodigiosin-HCl (cPrG-HCl) was used to investigate the role of vacuole acidification in cereal aleurone cell function. The protein storage vacuole (PSV) becomes acidified rapidly when aleurone cells are treated with gibberellic acid (GA) but not abscisic acid (ABA). We show that cPrG prevents PSV acidification in aleurone layers and prevents synthesis of secretory proteins such as alpha-amylase. Our data support the hypothesis that decreased hydrolase synthesis is a consequence of decreased hydrolysis of storage proteins in PSV. Support for this hypothesis comes from experiments showing that breakdown of barley 7S globulins and phytate is inhibited by cPrG in GA-treated aleurone layers. Decreased mobilization of PSV reserves is accompanied by reductions in the free amino acid pool size and in the amount of ions released from the aleurone layer. Vacuolation of the aleurone cell is a diagnostic feature of the response to GA, and vacuolation is also inhibited by cPrG. Evidence that cPrG acts as a potential H+/Cl- symporter in aleurone is presented. We show that cPrG does not inhibit the synthesis and secretion of alpha-amylase when Cl- ions are omitted from the incubation medium. Although cPrG blocks many GA-induced responses of aleurone layers, it does not affect early steps in GA signaling. The SLN1 protein, a negative regulator of GA signaling, is turned over in GA-treated cells in the presence and absence of cPrG. Similarly, synthesis of the transcriptional activator GAMYB is unaffected by the presence of cPrG in GA-treated cells.
假定的H⁺/Cl⁻同向转运体环丙基灵-盐酸盐（cPrG-HCl）被用于研究液泡酸化在谷物糊粉层细胞功能中的作用。当用赤霉素（GA）而非脱落酸（ABA）处理糊粉层细胞时，蛋白质储存液泡（PSV）会迅速酸化。我们发现cPrG可阻止糊粉层中PSV的酸化，并阻止分泌蛋白如α-淀粉酶的合成。我们的数据支持这样的假说，即水解酶合成减少是PSV中储存蛋白水解减少的结果。对这一假说的支持来自实验，这些实验表明在GA处理的糊粉层中，cPrG可抑制大麦7S球蛋白和肌醇六磷酸的分解。PSV储备物质的动员减少伴随着游离氨基酸库大小的减小以及从糊粉层释放的离子量的减少。糊粉层细胞的液泡化是对GA反应的一个诊断特征，并且液泡化也受到cPrG的抑制。文中给出了cPrG在糊粉层中作为潜在的H⁺/Cl⁻同向转运体发挥作用的证据。我们发现当在孵育培养基中省略Cl⁻离子时，cPrG不会抑制α-淀粉酶的合成与分泌。尽管cPrG阻断了糊粉层许多GA诱导的反应，但它不影响GA信号传导的早期步骤。SLN1蛋白是GA信号传导的负调节因子，在有或没有cPrG存在的情况下，它在GA处理的细胞中都会被降解。同样，转录激活因子GAMYB的合成在GA处理的细胞中不受cPrG存在的影响。
