Isolation and Expression Analysis of a Defensin Gene from Strawberry (Fragaria×ananassa cv. Paros)

Plant defensins are the cysteine-rich peptides that are encoded by small multi-gene families in the plant kingdom. In this study, we designed primers based on conserved regions of defensin genes to clone and identify defensin genes in strawberry (Fragaria×ananassa cv. Paros) by reverse transcription PCR technique. Sequence analysis showed that the deduced amino acid had significant similarity to other plant defensins from NCBI database and designated FaDef1. The predicted strawberry defensin protein encodes a 54 aa protein of 6.18 kDa, pI 9.22 and eight conserved cysteine residues with desired space conservation with other amino acids. Semi quantitative expressions of FaDef1 were analyzed in root, stem, leaf, flower, and fruit in three strawberry cultivars, namely, Queenelisa, Camarosa, and Paros. The results showed that the FaDef1 expression patterns were similar in different tissues of the three cultivars. The higher amount of relative expression of FaDef1 was in fruit and there was no observable expression in the root. The expression of FaDef1 increased after wounding and salicylic acid treatment. The expression level was higher in developed fruits compared to that of immature fruits. In fruits infected with the Gray mold agent (Botrytis cinerea), the expression of FaDef1 showed significant increase by development of disease symptom. Taken together, these results suggest that FaDef1 is both responsive to biotic stress signal compounds and strawberry B. cinerea and may be used as a candidate gene for engineering plants against gray mold.