Over-expression of a transcription factor mEmBP-1a increases rice photosynthesis, biomass and yield by regulating the expression of multiple key photosynthesis genes

Improvement in the photosynthetic efficiency is a major approach to improve crop yield potential. So far, most of the demonstrated cases of photosynthesis improvement was achieved through manipulation of one or a few photosynthesis related genes. Present study found that over-expression of one maize transcription factor, mEmBP-1 gene, led to simultaneously increased expression of nearly all genes in photosynthesis pathway, including genes encoding chlorophyll a and b-binding proteins (Lhca and Lhcb), photosystem II (PsbR3 and PsbW) and PS I reaction center subunits (PsaK and PsaN), genes encoding for chloroplast ATP synthase subunit and electron transport reaction (Fd1 and PC), and also major genes in the Calvin Benson Bassham cycle, Rubisco, GAPDH, FBA, TK and PRK. This increased photosynthesis gene expression resulted in increased leaf chlorophyll pigment, photosynthetic rate, quantum yields, biomass growth and grain yield both in the greenhouse and also in natural field conditions. Using DNA-Protein binding experiment, we found that mEmBP-1a protein can directly bind to the promoter regions of photosynthesis genes, suggesting that the direct binding of mEmBP-1a to the G-box domain of photosynthetic genes upregulates expression of these genes. Hence, this study shows that mEmBP-1a is a major regulator of photosynthesis. Overall design: For RNA-sequencing (RNA-seq) analysis, we collected the top second leaves of mEmBP-OE-4 line and WT at early heading stage at about 10:00 a.m. from field grown plants. Four replications of mEmBP-OE-4 line (mEmBP-OE-4_rep1-4) and WT (WT_rep1-4) were collected, respectively. RNA was extracted using the PureLink RNA Mini Kit following manufacturer's protocol (Life Technologies Corporation). RNA libraries were prepared for sequencing based on standard Illumina protocols and sequenced using Ilumina X Ten platform in paired-end 150 mode.