Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany.
University of Potsdam, Institute of Biochemistry and Biology, 14476 Potsdam-Golm, Germany.
Plant Physiol. 2018 Jul;177(3):1286-1302. doi: 10.1104/pp.18.00292. Epub 2018 May 14.
Leaf senescence is an essential physiological process in plants that supports the recycling of nitrogen and other nutrients to support the growth of developing organs, including young leaves, seeds, and fruits. Thus, the regulation of senescence is crucial for evolutionary success in wild populations and for increasing yield in crops. Here, we describe the influence of a NAC transcription factor, SlNAP2 ( NAC-like, activated by Apetala3/Pistillata), that controls both leaf senescence and fruit yield in tomato (). expression increases during age-dependent and dark-induced leaf senescence. We demonstrate that SlNAP2 activates (), a homolog of Arabidopsis () , chlorophyll degradation genes such as ( senescence-inducible chloroplast stay-green protein 1) and ( pheide oxygenase), and other downstream targets by directly binding to their promoters, thereby promoting leaf senescence. Furthermore, SlNAP2 directly controls the expression of genes important for abscisic acid (ABA) biosynthesis, 9-cis-epoxycarotenoid dioxygenase 1 (); transport, ABC transporter G family member 40 (); and degradation, ABA 8'-hydroxylase (), indicating that SlNAP2 has a complex role in establishing ABA homeostasis during leaf senescence. Inhibiting expression in transgenic tomato plants impedes leaf senescence but enhances fruit yield and sugar content likely due to prolonged leaf photosynthesis in aging tomato plants. Our data indicate that SlNAP2 has a central role in controlling leaf senescence and fruit yield in tomato.
叶片衰老（leaf senescence）是植物的一种重要生理过程，它支持氮和其他营养物质的再循环，以支持发育器官（包括幼叶、种子和果实）的生长。因此，衰老的调节对于野生种群的进化成功和作物产量的提高至关重要。在这里，我们描述了一个 NAC 转录因子 SlNAP2（NAC-like，由 Apetala3/Pistillata 激活）的影响，它控制番茄中的叶片衰老和果实产量。SlNAP2 的表达在年龄依赖和黑暗诱导的叶片衰老过程中增加。我们证明 SlNAP2 通过直接结合其启动子来激活 SlHY5（Arabidopsis 的 HY5 的同源物），从而激活叶绿素降解基因，如 SlPSI（衰老诱导的叶绿体保持绿色蛋白 1）和 SlPAO（pheide 加氧酶），以及其他下游靶标，从而促进叶片衰老。此外，SlNAP2 直接控制参与脱落酸（ABA）生物合成的基因的表达，如 SlNCED1（9-cis-epoxycarotenoid dioxygenase 1）；运输，SlABCG40（ABC 转运蛋白 G 家族成员 40）；和降解，SlABA8'-羟化酶（ABA 8'-hydroxylase），这表明 SlNAP2 在叶片衰老过程中建立 ABA 动态平衡中具有复杂的作用。在转基因番茄植物中抑制 SlHY5 的表达会阻碍叶片衰老，但会增强果实产量和糖含量，这可能是由于衰老番茄植株中叶片光合作用的延长。我们的数据表明，SlNAP2 在控制番茄叶片衰老和果实产量中具有核心作用。
