自毒胁迫对甜瓜种子萌发与幼苗保护酶活性和转录组的影响
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引用本文:张志忠,奚玉培,韩晓云,王革伏.自毒胁迫对甜瓜种子萌发与幼苗保护酶活性和转录组的影响[J].西北植物学报,2019,39(12):2197~2206
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作者单位
张志忠1,奚玉培1,韩晓云1,王革伏1, 2 (1 福建农林大学 园艺学院福建农林大学 戴尔豪西大学联合实验室福州 3500022 加拿大戴尔豪西大学 农学院加拿大特鲁罗 N2B 5E3) 
基金项目:国家重大农技推广服务试点项目(KNJ 152046);
中文摘要:甜瓜自毒作用是导致其栽培实践中连作障碍严重的关键原因之一。该实验以甜瓜植株水浸提液处理模拟甜瓜自毒胁迫,通过测定自毒条件下甜瓜种子萌发、幼苗根系保护酶活性和MDA含量的变化及转录组分析,以探讨甜瓜自毒作用机理。结果显示:(1)甜瓜自毒胁迫总体上抑制了甜瓜种子萌发和后续生长,胁迫处理的阈值为0.03 g/mL。(2)甜瓜植株水浸提液处理后其幼苗根系保护酶活性和MDA含量变化非常剧烈,SOD活性表现为降 升 降趋势,POD活性先降后升,CAT活性先升后降,MDA含量持续增加。(3)转录组分析结果共鉴定出2 599个差异表达基因(differentially expressed genes, DEGs),胁迫2 d后共产生2 251个DEGs,显著多于胁迫4 d后的329个DEGs;且2 d与0 d对比有923个DEGs上调,1 328个DEGs下调,表明甜瓜幼苗在基因水平对自毒胁迫产生了积极响应。(4)相关生物信息学分析表明,自毒胁迫导致的DEGs主要与苯丙烷代谢、活性氧代谢、光合作用和植物激素信号转导有关,同时也涉及到渗透调节、膜和蛋白保护等过程;且这些DEGs主要富集于2 d 与 0 d,说明自毒胁迫条件下幼苗光合作用发生了改变,且这种变化主要发生在胁迫早期。(5)对6个甜瓜自毒胁迫密切相关DEGs(AP2 2、bZIP1、bZIP2、AP2 1、bHLHHIS)的qRT PCR分析显示,AP2 1、bHLHHIS等3个基因在自毒胁迫2 d时表达量出现峰值,对照组AP2 2基因在2 d时表达量达到峰值,结果与转录组测序分析结果一致。研究表明,甜瓜自毒胁迫引起了其植物细胞的异常,进而会对生长和器官结构产生不良影响并诱发了大量与刺激或胁迫相关的基因差异表达,且甜瓜自毒胁迫下短期响应的基因或转录因子数量明显多于长期响应的数量,暗示甜瓜幼苗可以对自毒胁迫做出快速响应。
中文关键词:甜瓜  自毒作用  转录组分析  保护酶  植株水浸提液
 
Effects of Autotoxicity on Seed Germination, Protective Enzyme Activity and Transcriptome of Melon Seedlings
Abstract:Autotoxicity is one of the key reasons for serious continuous cropping obstacles in melon cultivation. In this experiment, the aqueous extract of melon plant was used to simulate the autotoxicity stress of melon. The mechanism of melon autotoxicity was investigated by measuring the changes of seed germination, protective enzyme activity and MDA content in root of melon seedlings and transcriptome analyses under autotoxicity stress. The results showed that: (1) the autotoxicity inhibited the germination and subsequent growth of melon seeds, and 0.03 g/mL plant aqueous extract was the threshold value of autotoxicity stress. (2) The activities of protective enzymes and MDA content changed dramatically in root of melon seedlings after treated by melon plant aqueous extracts. SOD activity decreased first, then increased and then decreased. POD activity decreased first and then increased, CAT activity increased first and then decreased and MDA content continued to increase. (3) Transcriptome analysis identified 2 599 differentially expressed genes (DEG) related to melon autotoxicity. There were 2 251 DEGs on 2 d after stress, significantly more than 329 on 4 d. 923 DEGs were up regulated and 1 328 were down regulated in 2 d compared with 0 d. (4) The results showed that melon seedlings had a positive response to autotoxicity at the gene level. Relevant bioinformatics analysis showed that the DEGs caused by autotoxicity were mainly related to phenylpropanoid metabolism, reactive oxygen species (ROS) metabolism, photosynthesis and plant hormone signal transduction, as well as gene differential expression in osmotic regulation, membrane and protein protection. Moreover, these DEGs were mainly enriched in 2 d and 0 d, indicating that photosynthesis of seedlings changed under autotoxicity stress, and this change mainly occurred in the early stage of stress. (5) Six DEGs closely related to melon autotoxicity, AP2 2, bZIP1, bZIP2, AP2 1, bHLH and HIS, were analyzed by qRT PCR. The results showed that the expression of AP2 1, bHLH and HIS reached the peak at 2 d, and AP2 2 peaked at 2 d in the control group, which were consistent with the results of transcriptome analysis results. The results showed that autotoxicity of melon caused the abnormality of plant cells, and then deteriorated the growth and the formation of organ structure. At the same time, a large number of DEGs related to stimulation or stress were induced. The number of short term response genes or transcription factors was significantly higher than that of long term response under autotoxicity stress, suggesting that melon seedlings can respond quickly to autotoxicity stress.
keywords:melon  autotoxicity  transcriptome analysis  protective enzyme  plant aqueous extracts
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