High starch accumulation mechanism and phosphorus utilization efficiency of duckweed (Landoltia punctata) under phosphate starvation

Abstract

Phosphorus is an essential element for plant growth and reproduction. This study aimed to investigate the metabolic response, growth, and starch accumulation mechanisms in duckweed strain, Landoltia punctata 0202, under phosphate starvation. The results revealed that, under phosphate starvation, the total phosphorus in L. punctata 0202 decreased, while total carbon increased. After 15 days of phosphate starvation, biomass yield increased from 12.64 to123.87 g m−2, while phosphorus utilization efficiency increased to 761.78 g g−1. The starch content accumulated from 2.14 to 38.05 % by Day 15, and the starch yield reached 47.14 g m−2 on Day 15. Furthermore, biochemical and transcriptome analysis results showed a sharp increase in ADP-glucose pyrophosphorylase activity and the expression of genes encoding granule starch synthase and starch branching enzyme under phosphate starvation supported starch accumulation in L. punctata 0202. Additionally, large amounts of high-affinity phosphate transporters, vacuolar phosphate efflux transporters, and purple acid phosphatases were expressed. In summary, based on multi-level physiological and biochemical results, transcriptomic analyses, and preliminary analysis of the phosphate efflux transporter protein function, this study revealed the mechanism of starch accumulation induced by phosphate starvation and high-efficiency phosphate recycling in L. punctata. These findings offer an important foundation and insight into the molecular mechanisms influencing the uptake and utilization of nutrients. The screened functional genes exhibited potential for crop improvements under stressful environmental conditions.