番木瓜NAC转录因子的克隆与表达分析

Cloning and Expression Analysis of NAC Transcription Factor from Carica papaya

为探究番木瓜NAC转录因子的序列特征及功能,以‘大庆7号’番木瓜果肉为试验材料,采用RTPCR克隆出2个不同的NAC类基因,命名为CpNAC1(Gene Bank KT364871)和CpNAC2(Gene Bank KT372241),其开放阅读框(ORF)长度分别为609 bp和805 bp,分别编码202个和268个氨基酸,其N端含有NAM保守结构域。采用实时荧光定量PCR研究其在乙烯利及清水对照处理后果实不同成熟时期中的表达情况,结果发现,CpNAC1和CpNAC2基因随着处理后时间的增加,表达量呈先下降后缓慢上升的趋势,且均与果实成熟呈负相关。但CpNAC1表达趋势与果实成熟过程中乙烯的表达量相反,受乙烯抑制降低表达量,从而参与了番木瓜果实的成熟衰老进程,而CpNAC2基因在乙烯处理后番木瓜果实中表达量与对照处理相比没有显著变化,说明CpNAC2基因不是通过乙烯信号传导途径来调控果实成熟。

In the present study, two novel NA C genes encoding NAC proteins in papaya, CpNA C1 and CpNA C2 were isolated from papaya fruit. The length of the cDNAs of CpNAC1 and CpNAC2 was 609 bp and 805 bp, encoding 202 and 268 predicted amino acids, respectively. Sequence analysis demonstrated that the CpNAC1 and CpNAC2 proteins contained NAM consecutive structural domain of the NAC superfamily. RT-qPCR analysis demonstrated that the expressing level of CpNAC1 and CpNAC2 dropped first and slowly increased afterward, and was negatively correlated with fruit mature. But the expression of CpNAC1 decreased significantly after ethephon treatment, indicating that CpNAC1 may be related to ethylene signal tansduction pathway. And CpNAC2 transcript levels had no change during ethephon treatment compared to the controls. These results suggests that the expression of CpNA C2 decrease in papaya fruit ripening and softening was not induced by ethylene.