CHANGES IN GENE EXPRESSION OF HARVESTED CABBAGE IN RESPONSE TO MECHANICAL WOUND STRESS

Mechanical stress, imposed on plant cells by a variety of physical stimuli during harvesting and handling of fresh horticultural products, induces a wide range of cellular responses through cellular receptor, signal transduction, and gene activation. To understand response behavior of cabbage to mechanical stresses (wounding and dropping), the characteristics of gene expression related to stress signal transduction and cellular response of cabbage were investigated. Quantitative real-time PCR data showed that candidate stress-responsive genes responded differently to specific stress application. The wounding treatment (punching the cabbage leaf by a cork borer) significantly induced the transient expression of calmodulin (CaM)-encoding genes, BoCam1 and BoCam2, within an hour after the treatment. These genes are considered to be involved in stress signal cascades in plant cells, including cabbage. The increased expression of phospholipase D (PLD)-encoding genes, BoPLD1 and BoPLD2, was also detected after the treatment. In response to the wound stress, the expression of BoCam1 and BoPLD2 appeared to be highly induced than that of BoCam2 and BoPLD2, respectively. The dropping treatment (letting the cabbage head dropped from a height of 40 cm against a cork) predominantly induced the BoCam1, BoCam2, BoPLD1, and BoPLD2 expression. Additionally, the prolonged and increased expression characteristics of genes were observed in wounded cabbage caused by dropping treatment. In conclusion, CaM-encoding genes and PLD-encoding genes are likely to be wound-responsive that are induced to high expression levels after encountering stresses. Moreover, because of their predominant response to the mechanical stresses, CaM-encoding genes and PLD-encoding genes should be taken into consideration in further study of postharvest mechanical stresses as it may be associated with the signaling cascade and cellular stress response in cabbage.