Overexpression of MdIPT8 Encodes an Isopentenyl Transferase Enzyme Enhances Resistance to Colletotrichum Gloeosporioides in apple (Malus Domestica)

Abstract

Apple (Malus domestica) is a delicious fruit and have high economic value. However, numerous destructive fungi affect apple tree and limit the development of apple production. Many researches showed that salicylic acid and jasmonic acid improved plant resistance to fungal disease, but the potential mechanisms between cytokinin and fungal disease were hardly reported. The IPT gene family encodes the proteins of synthetizing cytokinin and plays an indispensable role in plant biological stress. In our previous study, we found the disease resistance in autotetraploid apple was much better than ‘Hanfu’ and we analyze the gene expression in ‘Hanfu’ and autotetraploid apple. We found the MdIPT8 gene was significantly different expressed. Therefore, we focused on MdIPT genes. We uncovered ten IPT genes in the ‘Hanfu’ whole genome, that are unevenly distributed across five chromosomes. Phylogenetic analysis indicated this family falling into two groups. Moreover, the transcriptional analysis of ten IPT genes indicated MdIPT8 can be induced under Colletotrichum gloeosporioides stress stimulating in apple leaves. The MdIPT8 protein coalesced to green fluorescent protein pinpointed to the chloroplast. Finally, we confirmed that the overexpression of MdIPT8 increased resistance to C. gloeosporioides. Additionally, the endogenous cytokinin content of ‘Hanfu’ leaves increased under the stress of C. gloeosporioides and exogenous cytokinin improved the disease resistance of leaves. Our findings supply an overview of the identification of apple IPT gene family and increases the understanding of cytokinin in apple anthracnose resistance study.