Mahmood Kashif, El-Kereamy Ashraf, Kim Sung-Hyun, Nambara Eiji, Rothstein Steven J
Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
Present address: Division of Agriculture and Natural Resources, University of California, Cooperative Extension Kern County, Bakersfield, CA, USA.
Plant Cell Physiol. 2016 Oct;57(10):2029-2046. doi: 10.1093/pcp/pcw120. Epub 2016 Jul 7.
Members of the NAC transcription factor family have been implicated in the regulation of different processes of plant development including senescence. In this study, the role of ANAC032 is analyzed in Arabidopsis thaliana (Col-0). ANAC032 is shown to act as a transcriptional activator and its expression is induced in senescing leaves as well as in dark-treated detached leaves. Analysis of transgenic overexpressors (OXs) and chimeric repressors (SRDXs) of ANAC032 indicates that ANAC032 positively regulates age-dependent and dark-induced leaf senescence. Quantitative real-time PCR analysis showed that ANAC032 regulates leaf senescence mainly through the modulation of expression of the senescence-associated genes AtNYE1, SAG113 and SAUR36/SAG201, which are involved in Chl degradation, and ABA and auxin promotion of senescence, respectively. In addition, ANAC032 expression is induced by a range of oxidative and abiotic stresses. As a result, ANAC032 overexpression lines exhibited enhanced leaf senescence when challenged with different oxidative (3-aminotriazole, fumonisin B1 and high light) and abiotic stress (osmotic and salinity) conditions compared with the wild type. In contrast, ANAC032 SRDX lines displayed the opposite phenotype. ANAC032 transgenic lines showed altered 2,4-D-mediated root tip swelling and root inhibition responses when compared with the wild type. The altered response to auxin, oxidative and abiotic stress treatments in ANAC032 transgenic lines involves differential accumulation of HO compared with the wild type. Taken together, these results indicate that ANAC032 is an important transcription factor that positively regulates age-dependent and stress-induced senescence in A. thaliana by modulating reactive oxygen species production.
NAC转录因子家族成员参与调控植物发育的不同过程，包括衰老。在本研究中，对拟南芥（Col-0）中ANAC032的作用进行了分析。结果表明，ANAC032作为转录激活因子发挥作用，其表达在衰老叶片以及黑暗处理的离体叶片中被诱导。对ANAC032转基因过表达植株（OXs）和嵌合抑制子（SRDXs）的分析表明，ANAC032正向调控年龄依赖性和黑暗诱导的叶片衰老。定量实时PCR分析表明，ANAC032主要通过调节衰老相关基因AtNYE1、SAG113和SAUR36/SAG201的表达来调控叶片衰老，这些基因分别参与叶绿素降解以及脱落酸和生长素对衰老的促进作用。此外，ANAC032的表达受一系列氧化和非生物胁迫诱导。因此，与野生型相比，ANAC032过表达株系在受到不同氧化胁迫（3-氨基三唑、伏马菌素B1和高光）和非生物胁迫（渗透胁迫和盐胁迫）时，叶片衰老增强。相反，ANAC032 SRDX株系表现出相反的表型。与野生型相比，ANAC032转基因株系对2,4-D介导的根尖肿胀和根抑制反应发生改变。ANAC032转基因株系对生长素、氧化和非生物胁迫处理的反应改变涉及与野生型相比HO的差异积累。综上所述，这些结果表明，ANAC032是一个重要的转录因子，通过调节活性氧的产生正向调控拟南芥中年龄依赖性和胁迫诱导的衰老。
