Expression pattern and structural analysis of AGAMOUS-LIKE 6 (AGL6) in Iranian garlic clones (Allium sativum L.)

Most of the garlic clones are non-bolting and sterile and propagate asexually; however, some of the clones are bolting, and there are some fertile clones among the bolting ones. A correct understanding of the MADS-BOX genes family expression pattern and structure, including AGL6, is a valuable project and will improve garlic breeding programs. So far there are no reports relating AGL6 identification as a flowering and fertility integrator gene in garlic. So the aim of this study is to investigate the relative expression of AGL6 in Iranian bolting, semi- and non-bolting garlic clones and to identify its structure and nucleotide sequence.

At first the relative expression of the AGL6 was investigated in the different organs of non-bolting, semi-bolting and bolting Iranian garlic clones using quantitative Real time- PCR. Then the isolation and cloning of the AGL6 partial sequences from the garlic floret was carried out using RT-PCR. The sequence of the recombinant plasmid was evaluated using BLAST, Vector NTI, ORF finder and MEGA6 software.

According to the obtained results, AGL6 was expressed in the meristem, inflorescence, tepal and carpel of green and purple flowers of the bolting garlic. But there was no sign of its expression in the stamen. AGL6 expression level in the meristem of bolting garlic was higher than the meristem of the semi-bolting and non-bolting garlic in all sampling stages, especially in the flowering induction stage. AGL6 was also expressed in the inflorescence of the semi-bolting and bolting garlic, but its expression in the inflorescence of the semi- bolting garlic was 4 times less than the inflorescence of the bolting garlic. Sequence analysis of the colonized fragment showed the coding region with a 728 bp length, which was registered in the NCBI database with the accession number of OK086759.1. This nucleotide sequence encodes a protein with 243 amino acids and has MADS-box and K-box domains. Results showed the high similarity of the sequence obtained in this research with other AGL6 gene homologues in other plant species, especially petaloid monocots such as onion, lily, narcissus and saffron in NCBI. Hence the resulting sequence was named AsAGL6.In this research, for the first time, the expression pattern of a key gene of the flowering and fertility pathway (AsAGL6) and its nucleotide structure were determined in garlic. The results of this research can be effectively used in the design of classical and molecular garlic breeding programs.