Abstract:

CitMYB22，an member of MYB family gene，was cloned using RT-PCR from leaf of Citrus junos Sieb. ex‘Ziyang’. Comparison between cDNA and genomic DNA sequences showed that two introns were existed in CitMYB22 gene. The 696 bp length ORF of CitMYB22，encoding a putative protein of 231 amino acids. The conserved R2R3 domain was observed in the amino acid structure sequence of CitMYB22. Phylogenetic analysis revealed that CitMYB22 shared the highest amino acid identities with homologous Arabidopsis R2R3-MYB transcription factor AtMYB15. A 2 500 bp long promoter of the CitMYB22 gene was isolated，sequence analysis showed that the promoter harbors multiple stress- responsive cis-elements，such as HSE，SARE and MYS. The green fluorescent protein transient expression assay revealed that the CitMYB22 protein was localized in nucleus location. qRT-PCR analysis indicated that the higher expression of CitMYB22 gene was in leaves and flowers than in roots and fruitlets. Moreover，CitMYB22 was induced by exogenous hormone abscisic acid（ABA），salicylic acid（SA），methyl jasmonate （MeJA），1-amino cyclopropane carboxylate（ACC）and physiological stresses of salinity，dehydration and low temperature（4 ℃）in leaves and roots. The results demonstrated that CitMYB22 may play a positive role in abiotic stress tolerance of citrus.

Key words: citrus, R2R3-MYB, stress, gene expression