External application of NADPH enhances biomass accumulation, seed germination and modulates expression of oxidative pentose phosphate pathway genes in Arabidopsis

NADPH is one of the main reducing powers in plant cells. It plays important roles as cofactor or reductant and is involved in a wide range of anabolic pathways and thus may influence plant growth and development. The present study was conducted with the objective to analyse the effect of NADPH on plant growth and development when applied externally. External application of 10 µM and 30 µM NADPH resulted in 198% and 258%, increase in biomass of Arabidopsis thaliana plants, respectively. Under normal photoperiod of 16 h, 24% increase in seed germination was observed in 10 µM as well as 30 µM NADPH treated seeds on day 8 of the seed sowing. Further, targeted transcriptome profiling of all the eight genes encoding enzymes of oxidative pentose phosphate pathway revealed the differential expression of these genes under light and dark in response to NADPH. Interestingly, expression of glucose-6-phosphate-1-dehydrogenase and 6-phosphogluconolactonase, the first two enzymes of oxidative pentose phosphate pathway was up-regulated many fold under dark, whereas, NADPH treatment significantly increased the expression of the 2nd (6-phosphogluconolactonase) and 3rd gene (6-phosphogluconate dehydrogenase) of oxidative pentose phosphate pathway during light period. Proteomic analysis revealed thirty five proteins expressing differentially in response to NADPH treatment. These differentially expressed proteins were found to be involved in various biological processes. To the best of our knowledge this is the first report about the effect of external application of NADPH on plant biomass and seed germination. The information generated in the present study may be useful in having better insights into the role and influence of NADPH on plant growth and development and may provide platform to devise NADPH associated strategies for improving biomass production of useful plants.