转录组与代谢组联合分析揭示遮阴胁迫下甘薯的代谢响应途径

Integrated analysis of transcriptome and metabolome reveals the metabolic response pathways of sweetpotato under shade stress

甘薯是喜光作物,但其在套种栽培模式中一般处于低位被遮阴,大田生长中后期也时常面临阴雨寡照天气而影响块根干物质积累,因此,解析甘薯在遮阴胁迫下的代谢响应途径可为其耐荫性品种改良提供理论依据。本研究对甘薯品种郑红23号进行透光率50%的遮阴胁迫15 d后发现,遮阴胁迫下郑红23号的叶绿素b以及总叶绿素含量较自然光照下均显著提高;叶绿素光系统PSII最大光化学效率(Fv/Fm)、PSII潜在活性(Fv/Fo)和光合性能综合指数(PIABS)在遮阴胁迫下均显著下降;净光合速率和水分利用率显著降低,SOD酶和POD酶活性则显著提高;此外,遮阴胁迫显著提高了郑红23号的蔓长和比叶面积,根鲜重则显著降低。对遮阴胁迫和自然光照条件下的叶片组织进行转录组和代谢组联合分析发现,差异基因和差异代谢物主要共同富集于苯丙素合成途径、糖代谢相关途径、鞘脂代谢途径和精氨酸合成途径。苯丙素合成途径富集到的上调差异表达基因多数为POD酶家族基因,说明遮阴胁迫触发了甘薯的ROS活性氧清除系统。同时,遮阴胁迫降低了甘薯植株的糖代谢水平,叶片可溶性糖含量下降,淀粉合成与降解均受到抑制,块根膨大受阻。而鞘脂及精氨酸代谢途径则可能通过提高生物膜的稳定性以及增加多胺类抗逆因子的合成底物来使植株更好地适应遮阴胁迫。以上结果为理解遮阴胁迫下甘薯的代谢响应途径提供了新的理论依据。

Sweetpotato is a heliophile crop.However,it is usually shaded in the lower position in the interplanting cultivation mode.During the middle and late field growing period,it often faces rainy weather with little illumination,which affects the dry matter accumulation in tuberous roots.Thus,analyzing the metabolic response pathways of sweetpotato under shade stress will provide the theoretical basis for the varieties’genetic improvement of shade tolerance.In this study,the sweetpotato variety Zhenghong 23 was exposed to shade stress with 50%light transmittance for 15 days.Results showed that chlorophyll b and the total chlorophyll contents of Zhenghong 23 under shade stress were significantly increased compared with those under natural light.The maximum photochemical efficiency(Fv/Fm),the potential activity(Fv/Fo),and the comprehensive index of photosynthetic performance(PIABS)of the chlorophyll photosystem PSII decreased significantly under shade stress.The net photosynthetic rate and water use efficiency decreased significantly,while SOD and POD enzyme activities increased significantly.In addition,shade stress increased significantly the vine length and specific leaf area of Zhenghong 23,but reduced significantly the fresh weight of roots.Transcriptome and metabolome analysis of leaf tissues under shade stress and natural light conditions showed that the DEGs and DMs were mainly enriched in phenylpropanoid biosynthesis,sugar metabolism,sphinolipid metabolism,and arginine biosynthesis pathways.Most of the up-regulated DEGs enriched in the phenylpropanoid biosynthesis pathway were POD enzyme family genes,indicating that the shade stress triggered the ROS scavenging system in sweetpotato.Meanwhile,shade stress reduced sugar metabolism level of sweetpotato,decreased the soluble sugar content of leaves,inhibited both the synthesis and degradation of starch,and blocked the expansion of tuberous roots.In addition,the sphinolipid and arginine metabolism pathways may better adapt sweetptoato plants to shade stress through improving the stability of biomembranes and increase the synthetic substrates of polyamine anti-stress factors.These results provide new theoretical basis for understanding the metabolic response pathways of sweetpotato under shade stress.