Transcriptomic and Metabolic Profiling Reveals ‘green Ring’ and ‘red Ring’ on Jujube Fruit Upon PostharvestAlternaria Alternatainfection

Alternaria alternata is the major threat to postharvest storage of jujube (Ziziphus jujuba Mill.) fruit. We found that natural A. alternata infection can cause very typical phenotype of 'green ring' and 'red ring' surrounding the disease spot on the jujube fruit. The phenotype was successfully modeled and constructed on jujubes by artificial inoculation with the pathogen. Furthermore, the pathogenic infection is evidenced essential to the onset of the phenotype. The 'red ring' circle is proved to be pre-fixed to block the 'green ring' area as a battlefield combating the pathogen's attack. We monitored the global transcriptomic profiling of 'green ring' and 'red ring' tissues from jujubes infected with A. alternata, in comparison with the mock-inoculated fruit and the control intact fruit. Large amount of differentially expressed genes were obtained in 'green ring', followed by 'red ring'. Transcriptional alterations associated with the core and peripheral phenylpropanoid and lignin pathways, plant hormonal metabolisms were greatly influenced in the 'green ring' and 'red ring' by the A. alternata infection. The integrated analysis of transcriptomic profiling and metabolic changes revealed the differentially but delicately coordinated activation of these biological processes in the 'green ring' and 'red ring' on jujubes in defensing the fungal infection.