Hydroxypyruvate reductase gene family in Nicotiana benthamiana: Genome-wide identification and expression pattern profiling

Hydroxypyruvate (HP), the key intermediate of photorespiration, is converted to glycerate via the catalysis of hydroxypyruvate reductases (HPRs) with NADH/NADPH as cofactors. The non-lethal phenotype resulting from HPR defects allows for the use of mutants to investigate interactions between photorespiration and other cellular processes, facilitating the establishment of plant chassis with compromised photorespiration. Considering that establishing a plant chassis of the HPR-series would provide great potential in promoting plant synthetic biology to tackle future challenges, the genome-wide identification and bioinformatics analysis of HPR gene family in N. benthamiana are imperative but remains to be solved. In this study, 12 N. benthamiana hydroxypyruvate reductases (NbHPRs) were identified from a genome-wide study. These genes could be classified into three subclasses by phylogenetic analysis, and conserved gene structures or motif compositions were identified in each subclass. A variety of signal-sensing elements were identified in the HPRs promoter regions indicating their regulation by multiple potential transcription factors such as C2H2 proteins. Quantitative real-time PCR (qRT-PCR) results further demonstrated the higher expression levels of NbHPRs in functional and young leaves compared to other organs. Subsequently, we confirmed the subcellular localization of NbHPRs with transient expression analysis, which suggests their different functions. Moreover, the relative expression level of the gene under nitrogen (N) treatment was assessed through qRT-PCR analysis. These works will offer valuable insights into elucidating the function and mechanism of HPRs in N. benthamiana, thus illuminating the strategies for introducing artificial carbon fixation pathways to tackle future challenges with the modification on photorespiration.