Genome-Wide Identification and Analysis of Respiratory Burst Oxidase Homolog (RBOH) Gene Family in Nelumbo nucifera.

Respiratory burst oxidase homologs (RBOHs) are core enzymes for reactive oxygen species (ROS) production in plants and play critical roles in stress signal transduction. In this study, we performed a genome-wide identification of the RBOH gene family in Nelumbo nucifera, comprehensively employed phylogenetic analysis, gene structure analysis, cis-acting element prediction, and other bioinformatics approaches, and examined their expression patterns under high-temperature stress using qRT-PCR. A total of ten NnRBOHs were identified, unevenly distributed across eight chromosomes. Phylogenetic analysis classified them into five subfamilies, with members within the same subfamily sharing highly similar gene structures and conserved motifs. The promoter regions contained abundant cis-acting elements associated with hormone, light, and stress responses. Under heat treatment, NnRBOHA and NnRBOHB were significantly upregulated, whereas the remaining NnRBOH family genes showed no significant changes in expression. These results indicate that different members of the NnRBOH family may play distinct roles during the heat-stress response. Collectively, this study clarifies the evolutionary characteristics of the NnRBOH family and identifies NnRBOHA as a potential key candidate gene for heat-tolerance genetic improvement, providing clear targets for subsequent functional validation and molecular breeding.