Abscisic acid (ABA) is a vital hormone that regulates stomatal closure and responds to stress conditions in plants. Therefore, ABA signal pathway involves numerous physiological processes in plants, such as seed dormancy, germination, development and ripening. Among the families of ABA receptor genes, ABA-insensitive (ABI) is a major transcription factor that regulates ABA signal pathway. To date, little information is known about the ABI gene of buckwheat.
To characterize ABI gene sequence polymorphism and genetic relationship of genus Fagopyrum, the budlets of 30 germplasm resources from seven wild species including F. esculentum, F. tataricum, F. zuogongense, F. pilus, F. megaspartanium, F. cymosum and F. urophyllum were collected for DNA extraction. The ABI UniGene sequence of buckwheat was isolated from the previously performed transcriptome sequencing data (accession number: SRS1350375). Specific primers of ABI gene were designed based on the high conservative sequence for polymerase chain reaction (PCR) amplification, and the amplified fragments from 30 germplasm resources were processed for gene sequencing. Then the gene sequence analysis was performed on nucleotide
BLAST of NCBI database (http://blast.ncbi.nlm.nih.gov/Blast.cgi), and the genetic variance was analyzed by DNAsp5, and the analysis of ClustalW multiple sequence alignment, genetic distance and hierarchy were clustered by MEGA 5.05.
The results showed that 20.28% of polymorphic sites were found in ABI gene fragments among 30 germplasm resources of the seven wild species of genus Fagopyrum, whereas only 1.86% of polymorphic sites were found among 14 germplasm resources of F. tataricum and 1.81% of polymorphic sites were found among five germplasm resources of F. esculentum, indicating that ABI gene sequence is highly conserved in the intraspecies of genus Fagopyrum. Genetic distance analysis showed that both the values of interspecific genetic distance and interspecific net genetic distance between F. zuogongense and F. pilus were the largest, whereas those between F. cymosum and F. urophyllum were the least based on the ABI gene sequence analysis. Hierarchical cluster analysis indicated that the phylogenetic relationship of F. tataricum was close to F. megaspartanium, F. cymosum and F. urophyllum, then further grouped with F. pilus, while the F. esculentum was close to F. zuogongense based on the ABI gene sequence analysis. The F. tataricum and F. zuogongense collected from different regions were respectively clustered, suggesting that the mutation of ABI gene might be influenced by the growth environment during plant evolution.
Inconclusion, ABI gene sequence is highly conserved in the intraspecies of genus Fagopyrum; nevertheless, different growth environments caused distinctive mutations of ABI gene. Based on the gene sequence analysis, a close relationship was found between F. esculentum and F. zuogongense. In addition, close relationships were also found among F. tataricum, F. megaspartanium, F. cymosum and F.urophyllum.The above results provide a theoretical basis for ABI gene research and evolutionary relationship of genus Fagopyrum, but the exact evolution among different species of buckwheat still needs further research.