Expression and regulation of the early auxin-responsive Aux/IAA genes during strawberry fruit development.

The plant hormone auxin transcriptionally activates Aux/IAA genes. Auxin plays an important role in regulating fruit growth and ripening of strawberry and Aux/IAA genes have been extensively studied in Arabidopsis, rice and tomato, but little information is available on strawberry fruit. In the present work, two full-length of early auxin-responsive Aux/IAA genes, termed FaAux/IAA1 and FaAux/IAA2 respectively, were isolated and characterized from strawberry fruit. Moreover, the expression profiles of two FaAux/IAA genes during fruit development, and the effect of naphthalene acetic acid (NAA) on their expressions of fruits at two different developmental stages were also investigated. The results showed that the levels of FaAux/IAA1 and FaAux/IAA2 transcripts were very high at early stage of fruit development, and decreased sharply at ripening stage (after white stage). In addition, NAA applied at the stage of large green and white fruit obviously increased the accumulations of FaAux/IAA1 and FaAux/IAA2 transcripts. These data suggested that the expressions of both FaAux/IAA1 and FaAux/IAA2 genes were likely to be involved in early fruit development, and the enhancement of FaAux/IAAs transcripts might be attributed at least or partially to auxin-induced fruit growth and delayed fruit ripening of strawberry.