Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/14/2014
Publication Date: 3/27/2014
Citation: Lv, J., Rao, J., Zhu, Y., Chang, X., Hou, Y., Zhu, Q. 2014. Cloning and expression of lipoxygenase genes and enzyme activity in ripening persimmon fruit in response to GA and ABA treatment. Postharvest Biology and Technology. 92:54-61. Interpretive Summary: Persimmon is an orphan species; therefore, limited genomic resources and molecular investigations specific to this crop are available when compared with other major perennial fruit crops such as apple, grape and citrus. The lipoxygenase (LOX) in the lipid peroxidation pathway has been studied for its roles in seed development, defense responses and plant volatile generation, while relatively few studies have focused on its regulating roles in the fruit ripening process. In this study the roles of two persimmon LOX genes, DkLox1 and DkLox3, were cloned and characterized during fruit ripening. Phylogenetic analysis on these two fruit-specific LOXs indicated that they both belong to 9-LOX sub-family. Their expression patterns and enzyme activities were shown to be closely associated with the changes of several fruit ripening indicators such as fruit firmness, ethylene production and MDA content. Their expression profiles under the treatments of ABA or GA suggested that their involvement in hormonal interactions during the fruit ripening process. While JA and many other oxylipins are considered as the primary defense signals in response to biotic and abiotic stresses, those oxylipins from the 9-LOX pathway in regulating fruit ripening is unclear. The data from this study provides direct evidence that other oxylipins from the 9-LOX branch, in addition to JA, could also actively regulate the persimmon fruit ripening process. The results from this study will help to unravel the genetic network regulating the ripening of persimmon fruit, a less s
Technical Abstract: Two genes of the lipoxygenase (LOX) family, DkLox1 and DkLox3 (GenBank accession No. JF436951 and JF436950), were cloned from persimmon fruit (Diospyros kaki L. ‘Fuping Jianshi’). Sequence analysis indicated that they belong to the 9-LOX sub-group. Heterologous expression of DkLox1 in E. coli produced a recombinant protein of about 118kDa in size. Transcriptional profiles of both LOX genes during fruit ripening and in response to gibberellin (GA3) and abscisic acid (ABA) treatments during postharvest storage were studied using quantitative reverse transcription PCR (qRT-PCR). The expression of DkLox1 and DkLox3 peaked at 12 days after the fruit were harvested and stored at room temperature, corresponding to the patterns of LOX activity, ethylene production, fruit softening and malondialdehyde (MDA) content. ABA treatment accelerated the persimmon fruit softening and ripening process, and the expression of DkLox1 and DkLox3 peaked 3 days earlier than the non-treated control. By contrast, the GA3 treatment decelerated the ripening process and down-regulated the expression of DkLox1 and DkLox3 genes. The roles of LOX gene expression during persimmon fruit ripening are discussed.