Study on the genetic diversity in NAC genes derived from peach cultivars with different ripening dates

NAC genes in plants play an important role in the plant development and the response to environmental stress. Furthermore, it was suggested that they may be involved in fruit development and determining ripening date in peach. The aim of this study was to clone the NAC gene from different ripening peach cultivars, and to analyze the structure characteristics in nucleotide and amino acid strands, trying to find a new clue for their possible roles in peach fruit development. Genomic DNA and total RNA were extracted from immature leaves collected from 11 peach cultivars, respectively. Then, the total RNA was reversely transcribed to cDNA. The primer pairs were designed based on NAC gene sequence in GDR database, and PCR was employed, then, products were cloned and sequenced. DNAMAN software was used to align nucleotide and amino acid sequences. ORF finder was used to search ORF and deduce amino acid sequences. CDD tool was used to analyze conserved domain in protein. Blastp tool was used to search homological proteins. Mega software was used to draw phylogenetic tree. There is a NAC domain in 16-140 amino acid strand. In N-terminal amino acid sequence of NAC domains is highly conserved, conversely, polymorphisms exist in the C-terminal. There are two types of mutation in nucleotide strand, i.e., SNP and Indel. A large amount of SNP and Indel appeared in the third Extron in cultivars 'Jinliuzaohong' and 'Xiaobaitao', which indicated unique structure in their NAC genes. Protein alignment revealed the highest homology between peach NAC and that in plum, a lesser one between peach and duck pear. The phylogenetic tree suggested the kin relationship. There are high level genetic polymorphisms among NAC gene derived from cultivars with different ripening dates. Mutations in conserved domain perhaps lead to change in protein functions.