Genome-wide surveys have also been performed in several species, e.g., seven members from grape ( Vitis vinifera), seven members from strawberry ( Fragaria × ananassa), nine members from rice ( Oryza sativa), nine members from cassava ( Manihot esculenta), ten members from arabidopsis ( Arabidopsis thaliana), ten members from rubber ( Hevea brasiliensis), and 15 members from wheat ( Triticum aestivum) ( Sagi & Fluhr, 2006 Cheng et al., 2013 Wang et al., 2013 Hu et al., 2018 Zhang et al., 2018 Zou & Yang, 2019a).
Since the first RBOH was characterized in rice ( Oryza sativa), a growing number of homologs have been identified in plant lineages ( Groom et al., 1996 Kaur et al., 2014). In higher plants, this enzyme is known as respiratory burst oxidase homolog (RBOH), which was characterized with the presence of one N-terminal NADPH_Ox domain, one Ferric reductase like transmembrane component, one FAD-binding domain, one NAD-binding domain, and several calcium-binding EF-hand motifs ( Sumimoto, 2008 Kaur et al., 2018). Respiratory burst oxidase, first identified in human phagocytic cells, is a key enzyme that catalyzes the production of superoxide from oxygen and NADPH ( Sumimoto, 2008). These findings will not only improve our knowledge on species-specific evolution of the Rboh gene family, but also provide valuable information for further functional analysis of Rboh genes in jatropha. Moreover, expression patterns of JcRbohs during flower development as well as various stresses were also investigated. Global gene expression profiling revealed diverse patterns of JcRbohs over various tissues. Although exon-intron structures are usually highly conserved between orthologs, loss of certain introns was observed for JcRbohB, JcRbohD, and RcRbohN, supporting their divergence. Conserved synteny and one-to-one orthologous relationship were observed between jatropha and castor bean Rboh genes. In contrast to a high number of paralogs present in arabidopsis and rice that experienced several rounds of recent whole-genome duplications, no duplicate was identified in both jatropha and castor bean. The family number of seven members identified from the jatropha genome is equal to that present in castor bean, and further phylogenetic analysis assigned these genes into seven groups named RBOHD, -C, -B, -E, -F, -N, and -H. This study presents a genome-wide analysis of Rboh family genes in jatropha ( Jatropha curcas) as well as the comparison with castor bean ( Ricinus communis), another economically important non-food oilseed crop of the Euphorbiaceae family. Compared with extensive studies in model plants arabidopsis and rice, little is known about RBOHs in other species. Respiratory burst oxidase homologs (RBOHs), which catalyze the production of superoxide from oxygen and NADPH, play key roles in plant growth and development, hormone signaling, and stress responses. Genomics analysis of genes encoding respiratory burst oxidase homologs (RBOHs) in jatropha and the comparison with castor bean. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited. 2 Hainan Key Laboratory for Biosafety Monitoring and Molecular Breeding in Off-Season Reproduction Regions, Key Laboratory of Biology and Genetic Resources of Tropical Crops, Ministry of Agriculture and Rural Affairs, Institute of Tropical Biosciences and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan, China DOI 10.7717/peerj.7263 Published Accepted Received Academic Editor Axel Tiessen Subject Areas Genomics, Molecular Biology, Plant Science Keywords Jatropha curcas, Ricinus communis, Rboh gene family, Phylogenetic analysis, Synteny analysis, Transcriptional profiling Copyright © 2019 Zhao and Zou Licence This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed.