类黄酮合成关键基因MeF3H在木薯块根采后腐烂中的功能分析

Functional analysis of MeF3H，a key gene for flavonoid synthesis，in cassava postharvest deterioration

关键词:  木薯  类黄酮  MeF3H  块根  采后腐烂

Key words:  cassava  flavonoids  MeF3H  tuberous roots  postharvest physiological deterioration

摘要:

为探究MeF3H在木薯块根采后生理腐烂（PPD）中的功能，以‘华南9号’（‘SC 9’）为试验材料，通过qRT-PCR技术分析MeF3H在叶片、叶柄、茎、脆性胚性愈伤组织（FEC）、花、腋芽、纤维根、块根及块根PPD中的表达情况，确定MeF3H的亚细胞定位，结合病毒诱导的基因沉默（virus-induced gene silencing，VIGS）分析MeF3H沉默后块根中类黄酮含量及块根腐烂情况。结果表明，MeF3H在腋芽及纤维根中高表达，MeF3H定位在细胞质，MeF3H基因表达及块根中类黄酮含量随着PPD程度加深而升高。qRT-PCR结果显示MeF3H沉默效率在39%~67%。MeF3H沉默后，与对照植株相比，沉默植株叶片及块根中类黄酮含量均显著下降（P<0.05），且MeF3H基因表达与块根中类黄酮含量呈显著正相关（P<0.05）。在采后储存第3天，块根超过50%的面积出现腐烂，而对照植株块根腐烂率为36.67%。综上，MeF3H表达与木薯块根中类黄酮含量及块根耐PPD能力存在显著正相关（P<0.05），MeF3H基因沉默后导致木薯块根PPD显著加速。

Abstract:

In order to understand the function of MeF3H in postharvest physiological deterioration （PPD） of cassava tuberous roots， ‘South China No. 9’ variety （‘SC 9’） was used as the material. The expression of MeF3H in leaves， petioles， stems， fragility embryogenic callus （FEC）， flowers， axillary buds， fibrous roots， tuberous roots and PPD process were analyzed， and the subcellular localization of MeF3H were determined. Virus induced gene silencing （VIGS） technology was used to silencing MeF3H， and the effects on flavonoid content and PPD were analyzed. The results showed that MeF3H was highly expressed in axillary buds and fibrous roots， and MeF3H was localized in the cytoplasm， the expression of MeF3H and content of flavonoid in tuberous roots were increased with PPD process. The results of qRT-PCR analysis indicated that the silence efficiency of MeF3H was 39% to 67%. Compared with control， the flavonoid content in the leaves and tuberous roots of silenced plants were significantly decreased（P<0.05）， and there is a significant positive correlation between MeF3H expression and flavonoid content（P<0.05）. The degree of PPD was significantly deepened in silenced cassava plants， with a root degeneration rate was over 50% at 3 d after harvest， while the deterioration rate in control plant was 36.67%. In conclusion， there is a significantly positive correlation between MeF3H expression and flavonoid content， PPD tolerance of turberus roots （P<0.05）. Silencing MeF3H gene significantly accelerates PPD occurrence in cassava tuberous roots.