ASCORBATE PEROXIDASE6 delays the onset of age-dependent leaf senescence
ASCORBATE PEROXIDASE6 delays the onset of age-dependent leaf senescence
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DOI：
10.1093/plphys/kiaa031
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发表时间：
2021-02-01
期刊：
影响因子：
7.4
通讯作者：
Miller, Gad
中科院分区：
文献类型：
--
作者：
Chen, Changming;Galon, Yael;Miller, Gad
活性氧（ROS）水平的年龄依赖性变化是叶片衰老的关键。过氧化氢酶和胞质抗坏血酸过氧化物酶（APX1）等h2o2还原酶严格控制衰老过程中的氧化负荷，但它们的调节和功能并不局限于衰老。在此之前，我们确定了抗坏血酸过氧化物酶6 （APX6）在拟南芥种子成熟过程中的作用。在这里，我们证明APX6是一个真正的衰老相关基因。APX6的表达在衰老叶片中被特异性诱导，并响应于促进衰老的刺激，如脱落酸（ABA）、延长的黑暗和渗透胁迫。Apx6突变体发育衰老早，对暗胁迫的敏感性增加。apx6突变体衰老前成熟绿叶中APX活性降低、H2O2水平升高、抗坏血酸库氧化还原状态改变与衰老早发相关。通过在烟叶中的瞬时表达分析，我们揭示了APX6的年龄依赖性转录后调控。然后，我们确定了APX6的编码序列作为miR398的潜在靶标，miR398是铜再分配的关键调节因子。此外，我们还发现，与野生型相比，SQUAMOSA启动子结合蛋白样7 （SPL7）突变体的APX6水平更高，而SPL7是铜稳态和miR398表达的主要调控因子，在缺铜条件下APX6水平进一步升高。我们的研究表明，APX6是衰老叶片中ROS/氧化还原稳态和信号的调节剂，在发育和应激诱导的衰老程序中起重要作用。
Age-dependent changes in reactive oxygen species (ROS) levels are critical in leaf senescence. While H2O2-reducing enzymes such as catalases and cytosolic ASCORBATE PEROXIDASE1 (APX1) tightly control the oxidative load during senescence, their regulation and function are not specific to senescence. Previously, we identified the role of ASCORBATE PEROXIDASE6 (APX6) during seed maturation in Arabidopsis (Arabidopsis thaliana). Here, we show that APX6 is a bona fide senescence-associated gene. APX6 expression is specifically induced in aging leaves and in response to senescence-promoting stimuli such as abscisic acid (ABA), extended darkness, and osmotic stress. apx6 mutants showed early developmental senescence and increased sensitivity to dark stress. Reduced APX activity, increased H2O2 level, and altered redox state of the ascorbate pool in mature pre-senescing green leaves of the apx6 mutants correlated with the early onset of senescence. Using transient expression assays in Nicotiana benthamiana leaves, we unraveled the age-dependent post-transcriptional regulation of APX6. We then identified the coding sequence of APX6 as a potential target of miR398, which is a key regulator of copper redistribution. Furthermore, we showed that mutants of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE7 (SPL7), the master regulator of copper homeostasis and miR398 expression, have a higher APX6 level compared with the wild type, which further increased under copper deficiency. Our study suggests that APX6 is a modulator of ROS/redox homeostasis and signaling in aging leaves that plays an important role in developmental- and stress-induced senescence programs.