Insights into pathogenicity variation in two genomes of Cercospora spp. causing gray leaf spot in maize.

Abstract

The gray leaf spots caused by Cercospora spp. severely affect the yield and quality of maize. However, the evolutionary relation and pathogenicity variation between species of the Cercospora genus is largely unknown. In this study, we constructed high-quality reference genomes by nanopore sequencing for two Cercospora spp., C. zeae-maydis and C. Zeina, with different pathogenicity collected from Northeast (Liaoning, LN) and Southeast (Yunnan, YN) China, respectively. The genome size of C. zeae-maydis-LN is 45.08 Mb containing 10,839 annotated genes, whereas that of Cercospora zeina-YN is 42.18 Mb containing 10,867 annotated genes, of which approximately 86.58% genes are common in the two species. The difference in their genome size is largely attributed to increased long terminal repeat (LTR) retrotransposons of 3.8 Mb in total length in C. zeae-maydis-LN. There are 41 and 30 carbohydrate-binding gene subfamilies identified in C. zeae-maydis-LN and C. zeina-YN, respectively. A higher number of CBM families found in C. zeae-maydis-LN, with unique CBM4, CBM37, and CBM66 in particular, may contribute to variation in pathogenicity between the two species as the carbohydrate-binding genes are known to encode cell wall degrading enzymes. Moreover, there are 114 and 107 effectors predicted, with 47 and 46 having unique potential pathogenicity in C. zeae-maydis-LN and C. zeina-YN, respectively. Of eight effectors randomly selected for pathogenic test, five were found to inhibit cell apoptosis induced by Bcl-2 Associated X. Taken together, our results provide genomic insights into variation in pathogenicity between C. zeae-maydis and C. zeina.