Functional Analysis of Histone ZmH2B in Regulating Maize Resistance to Bipolaris maydis

Maize histone ZmH2B belongs to the histone H2B family. In the current field of molecular biology, the majority of histone-related studies focus on their post-translational modification functions. However, studies specifically addressing histone H2B itself are relatively scarce, particularly concerning its response mechanism against Bipolaris maydis.In this study, a nucleus-localized ZmH2B was identified. To characterize the disease resistance phenotype of ZmH2B, we employed virus-induced gene silencing (VIGS) and transient overexpression (VOX) techniques to obtain ZmH2B-silenced material FoMV:ZmH2B and overexpressed material FoMV:ZmH2B-VOX. It was discovered that FoMV:ZmH2B promoted the infestation of B. maydis and inhibit the reactive oxygen species (ROS) burst induced by chitin. Conversely, FoMV:ZmH2B-VOX exhibited the opposite effects. Furthermore, ZmH2B was verified to positively regulate the infestation of B. maydis through pathogenesis-related (PR) genes. Subsequently, transcriptome analysis was carried out on the ZmH2B-silenced material and the differentially expressed genes were predominantly enriched in photosynthesis-related pathways.Collectively, these results suggested that ZmH2B plays a positive role in regulating maize resistance to B. maydis. The fourth leaves of maize plants with virus-induced silencing of ZmH2B or EV and T2 transgenic maize plants overexpressing ZmEIP1 and WT plants were collected for total RNA extraction and RNA-seq library construction. The RNA-seq libraries were sequenced on an Illumina HiSeq platform in paired-end mode with a read length of 150 bp (Novogene, Beijing, China). The raw reads were filtered using ht2-filter in the HTQC package (1.92.1) with default parameters to remove low-quality reads. The filtered reads were compared to the reference maize genome (Zea mays RefGen_V4) using TopHat (2.0.11) to remove host genome sequences. The mapped reads were assembled, and fragments per kilobase of transcript per million mapped reads (FPKM) values were calculated using Cufflinks. The Cufflinks output GTF file and the TopHat output BAM file were loaded into rMATS.3.2.2 to identify differential AS events. AS events with a P value < 0.05 were considered to be differential AS events.