Physiological and molecular basis of promoting leaf growth in strawberry (Fragaria ananassa Duch.) by CO2 enrichment

Abstract

Strawberry (Fragaria ananassa Duch.) is an economically important crop. Its yield is highly dependent on photosynthesis, and carbon dioxide (CO2) is one of the most important constituents in photosynthesis. In this study, we investigated the physiological and molecular mechanisms of CO2 enrichment in increasing strawberry leaf growth, and ultimately fruit yield. Strawberry plants were grown under ambient CO2 (350–500 μmol/mol) and elevated CO2 (750–850 μmol/mol) in a controlled environment. The results showed that CO2 enrichment significantly increased the size, net photosynthetic rate and light saturation point of the leaves, but decreased the light compensation point of leaves. Using RNA sequencing (RNA-Seq), transcriptome profiling of leaf tissues under two CO2 concentrations was conducted. The analysis identified 150 differentially expressed genes in response to increased CO2 concentration; 14 of them were shown to be involved in photosynthesis. Gene Ontology (GO) enrichment and pathways analyses revealed that CO2 enrichment enhanced the biosysthesis of metabolism-promoting growth hormones; sped up the reduction step of CO2 assimilation, and increased the transport of photosynthetic products, which help explain the increased net photosynthetic rate and accelerated leaf growth under elevated CO2 level. These results provide a valuable reference for exploring the mechanism of CO2 application in strawberry production in greenhouses especially during offseason.