Transcriptome profiling to elucidate mechanisms of the enhancement of the resistance to Botryosphaeria dothidea by nitric oxide in postharvest kiwifruit during storage

Nitric oxide (NO), as an important messenger in eukaryotes, is a novel chemical elicitor capable of inducing defense responses in fruit and vegetables. In this study, exogenous NO fumigation at a concentration of 15 mu l L-1 remarkably alleviated the disease symptoms of postharvest kiwifruit inoculated with Botryosphaeria dothidea. The disease incidence in the NO-treated kiwifruit was approximately 30%, 20%, and 13% lower than the control fruit from 4 to 6 days post inoculation. At 7 days after inoculation, the lesion size of the NO treated fruit was about 50% of that of the control fruit. Transcriptome analysis showed that 1275 genes (662 up-regulated and 613 down-regulated) were differentially expressed between NO-treated and control kiwifruit. Based on the functional information obtained, 46 of these genes are involved in pathogen-defense pathways. These key genes are associated with phenylalanine metabolism, mitogen-activated protein kinase signaling pathway, plant hormone signaling pathway, calcium ion signal decoding, and pathogenesis-related protein. Furthermore, the results of quantitative real-time polymerase chain reaction helped us to study the changes in the expression levels of candidate genes in different disease-resistant pathways. These results will help to understand the mechanisms of NO-induced pathogen resistance in postharvest kiwifruit.