马铃薯氮代谢对低氮胁迫的响应及转录组分析

Response of nitrogen metabolism of potato to low nitrogen stress and transcriptome analysis

【目的】探究不同氮效率马铃薯品种氮代谢对低氮胁迫的响应及分子机制,为马铃薯氮高效育种及高产栽培提供理论依据。【方法】以氮高效马铃薯品种冀张薯12号和氮低效马铃薯品种尤佳70为材料,采用盆栽试验方式,设置低氮(3 mmol/L纯氮)和正常施氮(15 mmol/L纯氮)处理,在出苗后30 d测定植株的干质量、氮积累量及氮代谢相关酶(硝酸还原酶(NR)、亚硝酸还原酶(NiR)、谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT))活性,并依托Illumina HiSeq 2000平台进行转录组测序分析。利用DESeq进行差异基因分析,通过GO富集和KEGG Pathway数据库注释参与马铃薯氮胁迫响应的差异表达基因。【结果】2种施氮量下冀张薯12号茎叶和根系的干质量、氮积累量以及NR、NiR、GS、GOGAT活性均高于尤佳70。与正常施氮相比,低氮胁迫下2个马铃薯品种茎叶和根系的干质量、氮积累量及叶片的NR和NiR活性均显著降低,根系的GS活性显著提高;尤佳70叶片的GS活性、GOGAT活性和根系的GOGAT活性均显著降低,冀张薯12号根系的NiR活性显著降低。转录组分析结果表明,在2个施氮量对比组中,尤佳70叶片和根系中的差异表达基因分别有6173个和249个,冀张薯12号叶片和根系中的差异表达基因分别有3455个和1990个。GO和KEGG结果显示,冀张薯12号的差异基因主要涉及氮代谢、氨基酸代谢等生物过程,尤佳70的差异基因主要涉及光合作用等生物过程。尤佳70和冀张薯12号根系中富集到氮代谢通路的差异基因分别有1个和8个,叶片中分别有11个和8个。尤佳70和冀张薯12号叶片的氨基酸相关代谢途径中涉及上调差异表达基因最多的均是苯丙氨酸代谢,其中编码苯丙氨酸解氨酶、肉桂酸-4-羟化酶、4-香豆酸-CoA连接酶的基因表达显著上调。【结论】在低氮条件下,氮高效品种冀张薯12号氮代谢相关酶活性较高,能减缓低氮胁迫对氮代谢的影响,进而保证较高的氮效率。

【Objective】This study explored the response and molecular mechanism of nitrogen metabolism of potato varieties with different nitrogen efficiencies to low nitrogen stress to provide basis for nitrogen-efficient breeding and high-yield cultivation.【Method】The nitrogen-efficient variety of Jizhangshu 12 and the nitrogen-inefficient variety of Youjia 70 were selected for pot experiments with low N treatment(3 mmol/L)and normal N application treatment(15 mmol/L).The dry mass,nitrogen accumulation,nitrate reductase(NR)activity,nitrite reductase(NiR)activity,glutamine synthetase(GS)activity and glutamate synthase(GOGAT)activity were measured 30 days after seedlings emerging,and the transcriptome sequencing was performed on Illumina HiSeq 2000 platform.DESeq was used for differential gene analysis.The GO and KEGG Pathway databases were used to analyze the differentially expressed genes involved in nitrogen stress.【Result】The dry mass,nitrogen accumulation,NR activity,NiR activity,GS activity and GOGAT activity of Jizhangshu 12 were higher than those of Youjia 70 under two nitrogen application rates.Compared to normal nitrogen application,the dry mass,nitrogen accumulation,leaf NR activity and NiR activity were significantly reduced and root GS activity was significantly increased by low nitrogen stress.The GS activity and GOGAT activity of leaves and GOGAT activity of roots in Youjia 70 were significantly reduced.The NiR activity of roots in Jizhangshu 12 was significantly reduced.The transcriptome analysis revealed 6173 differentially expressed genes in leaves and 249 differentially expressed genes in roots of Youjia 70.There were 3455 and 1990 differentially expressed genes in leaves and roots of Jizhangshu 12,respectively.The GO and KEGG analysis showed that the differentially expressed genes of Jizhangshu 12 mainly involved in biological processes such as nitrogen metabolism and amino acid metabolism,while the differentially expressed genes of Youjia 70 mainly involved in biological processes such as photosynthesis.There was 1 differentially expressed gene in the nitrogen metabolism pathway enriched in roots of Youjia 70 and there were 8 differentially expressed genes in Jizhangshu 12.There were 11 and 8 differentially expressed genes in leaves of Youjia 70 and Jizhangshu 12,respectively.Phenylalanine metabolism involved the most in the upregulation of differentially expressed genes in leaves of Youjia 70 and Jizhangshu 12,and the expressions of encoding phenylalanine aminase,cinnamate-4-hydroxylase and 4-coumarate-CoA ligase were significantly upregulated.【Conclusion】Under low-nitrogen conditions,the nitrogen-efficient variety of Jizhangshu 12 had higher activities for nitrogen metabolism-related enzymes to mitigate the effect of low-nitrogen stress on nitrogen metabolism and ensure high nitrogen efficiency.