Figure S5 from Evolutionary and functional analysis of the plant-specific NADPH oxidase gene family in <i>Brassica rapa</i> L.

NADPH oxidases (NOXs) have been known as respiratory burst oxidase homologues (RBOHs) in plants. To characterize the evolutionary relationships and functions of RBOHs in <i>Brassica rapa</i>, 134 <i>RBOH</i> homologues were identified from 13 plant species, including 14 members (namely <i>BrRBOH01</i>–<i>14</i>) from <i>B. rapa</i>. There presented 47 gene-pairs among 14 <i>BrRBOH</i>s and other <i>RBOH</i>s, consisting of five pairs within <i>B. rapa</i>, and 15 ones between <i>B. rapa</i> and <i>Arabidopsis thaliana</i>. Together with phylogenetic analysis, the results suggested that whole-genome duplication might have played an important role in <i>BrRBOH</i> gene expansion, and these duplication events occurred after the divergence of the eudicot and the monocot lineages examined. Furthermore, gene expression of <i>RBOH</i>s in both <i>A. thaliana</i> and <i>B. rapa</i> were assayed via qRT–PCR. An RBOH gene, <i>BrRBOH13</i> in <i>B. rapa</i>, was transformed into wild-type Arabidopsis plants. The transgenic lines with the overexpressed level of <i>BrRBOH13</i> conferred to be more tolerant to heavy metal lead (0.05 mM) than wild-type plants. Overall, this integrated analysis at genome-wide level has provided some information on the evolutionary relationships among plant-specific NOXs and the coordinated diversification of gene structure and function in <i>B. rapa</i>.