中波紫外线辐照对甜玉米种子萌发的影响及转录组分析

Effects of UV-B radiation treatment on seed germination of sweet maize and transcriptome analysis

【目的】研究中波紫外线(UV-B)辐照处理对甜玉米种子萌发及相关基因表达的影响,为解析UV-B辐照促进种子活力的分子机理奠定基础。【方法】以甜玉米自交系T28种子为材料,设置0(CK),0.5,1,2,4和8 h共6个不同时长的UV-B辐照处理,对处理和对照(CK)种子萌发相关的表型指标、生理指标进行分析,同时借助转录组测序技术筛选促进玉米种子萌发的差异表达基因。【结果】UV-B辐照处理1 h时甜玉米自交系T28种子的发芽率最高,发芽势、发芽指数和活力指数随着UV-B处理时间的延长均呈先上升后下降的趋势,且在UV-B辐照处理1 h时达到最高。UV-B辐照处理1和2 h的甜玉米种子萌发72 h后,萌发种子的CAT、POD活性和游离脯氨酸含量均高于CK。对0(CK),1和2 h辐照处理下的差异表达基因进行趋势表达分析,获得8个不同趋势的基因集profile(0-7),其中profile2中1 716个转录本表达量呈先下降后上升趋势,profile5中919个转录本表达量呈先上升后下降趋势。GO富集分析表明,在生物过程、细胞组分、分子功能类别中,profile2基因集中富集最显著的分别为蛋白磷酸化、膜整体组件、转移酶活性和转移己糖基,profile5基因集中富集为翻译、核糖体、核糖体的结构组分。KEGG富集分析发现,profile2基因集中显著富集的通路主要注释在苯丙素类生物合成、次生代谢物的生物合成、代谢途径等;profile5基因集中显著富集的通路为淀粉和蔗糖代谢、氧化磷酸化及蛋白酶体。淀粉和蔗糖代谢通路中13个基因与各样本表达量聚类分析表明,在处理1 h样本中这些基因的表达显著上调。【结论】UV-B处理可以提高甜玉米种子的活力,处理时长1 h的效果最显著,推测不同时长处理下的差异表达基因与种子活力密切相关。

【Objective】 The effects of ultraviolet(UV-B) irradiation on seed germination and related gene expression of sweet maize were studied to provide basis for analyzing molecular regulation mechanism of UV-B irradiation promoting seed activity.【Method】 Sweet corn inbred T28 seeds were selected with six UV-B radiation treatments of 0(CK),0.5,1,2,4 and 8 h durations.Phenotypic and physiological indexes of seeds in treatments and the CK were compared and analyzed,and the differentially expressed genes promoting seed germination were screened by transcriptome sequencing technology.【Result】 UV-B radiation for 1 h led to the highest germination rate of sweet corn inbred line T28 seeds,and germination potential,germination index and vigor index increased first and then decreased with the prolongation of UV-B treatment time with the highest values at 1 h.CAT and POD activities and free proline contents of seeds treated with UV-B irradiation for 1 and 2 h were higher than those of CK after 72 h germination.The trend expression analysis of differentially expressed genes under CK,1 and 2 h irradiation treatments obtained 8 gene set profiles(0-7) with different trends.A total of 1 716 transcripts in profile2 showed a trend of decreasing first and then increasing,and 919 transcripts in profile5 showed a trend of increasing first and then decreasing.GO enrichment analysis showed that protein phosphorylation,integral component of membrane,transferase activity and transfer hexose group of profile2 were most significantly enriched in biological processes,cell components and molecular function categories,respectively.The profile5 genes concentrated in structural components of translation,ribosomes,and structural constituent of ribosome.KEGG enrichment analysis showed that the significantly enriched pathways of profile2 gene set were mainly annotated in phenylpropanoid biosynthesis,biosynthesis of secondary metabolites and metabolic pathways,while those of profile5 gene set were starch and sucrose metabolism,oxidative phosphorylation and proteasome.The cluster analysis showed that the 13 genes in starch and sucrose metabolic pathways were significantly up-regulated in 1 h treatment.【Conclusion】 UV-B treatments improved germination and viability of sweet maize inbred T28 seeds with the best effects in 1 h treatment.It is speculated that differentially expressed genes under different treatment times were closely related to seed vigor.