Posttranslational Elevation of Cell Wall Invertase Activity by Silencing Its Inhibitor in Tomato Delays Leaf Senescence and Increases Seed Weight and Fruit Hexose Level
Posttranslational Elevation of Cell Wall Invertase Activity by Silencing Its Inhibitor in Tomato Delays Leaf Senescence and Increases Seed Weight and Fruit Hexose Level
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DOI：
10.1105/tpc.108.063719
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发表时间：
2009-07-01
期刊：
影响因子：
11.6
通讯作者：
Ruan, Yong-Ling
中科院分区：
文献类型：
--
作者：
Jin, Ye;Ni, Di-An;Ruan, Yong-Ling
蔗糖酶在植物发育中发挥着多种关键作用。因此，其活性必须在体内受到严格调控。新出现的证据表明，一组在体外抑制蔗糖酶活性的小蛋白质似乎存在于多种植物中。然而，人们对它们在植物中的作用知之甚少。在这里，我们检查了 INVINH1（一种假定的转化酶抑制剂）在番茄 (Solanum lycopersicum) 中的功能。 INVINH1：绿色荧光蛋白融合体的表达揭示了其质外质定位。拟南芥中 INVINH1 的异位过度表达特异性降低细胞壁转化酶活性。相比之下，沉默其在番茄中的表达显着增加了细胞壁转化酶的活性，而不改变细胞质和液泡转化酶的活性。 RNA干扰转基因番茄中细胞壁转化酶活性的升高导致（1）叶子寿命延长，从而阻止脱落酸诱导的衰老；（2）种子重量和果实己糖水平增加，这可能是通过增强果实脉管系统质外质中的蔗糖水解来实现的。这一论断基于 (1) INVINH1 和水果特异性细胞壁转化酶 Lin5 在幼果韧皮部薄壁细胞中的共表达，包括连接发育中种子的胎盘区域； (2)INVINH1和Lin5在体内的物理相互作用； (3)胎盘和种子之间界面处的共质不连续性。总之，结果表明，INVINH1 编码的蛋白质可特异性抑制细胞壁转化酶的活性，并通过限制植物中的转化酶活性来调节番茄叶片衰老以及种子和果实发育。
Invertase plays multiple pivotal roles in plant development. Thus, its activity must be tightly regulated in vivo. Emerging evidence suggests that a group of small proteins that inhibit invertase activity in vitro appears to exist in a wide variety of plants. However, little is known regarding their roles in planta. Here, we examined the function of INVINH1, a putative invertase inhibitor, in tomato (Solanum lycopersicum). Expression of a INVINH1: green fluorescent protein fusion revealed its apoplasmic localization. Ectopic overexpression of INVINH1 in Arabidopsis thaliana specifically reduced cell wall invertase activity. By contrast, silencing its expression in tomato significantly increased the activity of cell wall invertase without altering activities of cytoplasmic and vacuolar invertases. Elevation of cell wall invertase activity in RNA interference transgenic tomato led to (1) a prolonged leaf life span involving in a blockage of abscisic acid-induced senescence and (2) an increase in seed weight and fruit hexose level, which is likely achieved through enhanced sucrose hydrolysis in the apoplasm of the fruit vasculature. This assertion is based on (1) coexpression of INVINH1 and a fruit-specific cell wall invertase Lin5 in phloem parenchyma cells of young fruit, including the placenta regions connecting developing seeds; (2) a physical interaction between INVINH1 and Lin5 in vivo; and (3) a symplasmic discontinuity at the interface between placenta and seeds. Together, the results demonstrate that INVINH1 encodes a protein that specifically inhibits the activity of cell wall invertase and regulates leaf senescence and seed and fruit development in tomato by limiting the invertase activity in planta.