Differential effects of synthetic media on long-term growth, starch accumulation and transcription of ADP-glucosepyrophosphorylase subunit genes in Landoltia punctata

Abstract

AbstractMurashige & Skoog (MS) and Hoagland’s media were previously used forin vitroculture ofLandoltia punctata. During subsequentex vitroculture, the use of MS medium resulted in a higher growth rate, compared to Hoagland’s medium. Thus, a higher starch content ofL. punctatain MS medium was previously hypothesized. Here,L. punctatastrain 5632 was isolated and characterized using morphological characteristics and theatpF-atpHintergenic region. During early cultivation stage, fresh weight and relative growth rate in MS medium were lower than Hoagland’s medium. Conversely, starch content in MS medium was considerably higher than in Hoagland’s medium. Medium effects on expression of genes coding for starch-biosynthesis ADP-glucosepyrophosphorylase (AGPase) were determined. Genomic fragments of small (LeAPS) and large (LeAPL1) AGPase subunits were characterized. Differential expression between each AGPase subunit genes was observed in both media. Additionally, in MS medium, the highest correlation coefficients between starch content and gene expression was found withLeAPS(0.81) and followed byLeAPL3(0.67),LeAPL2(0.65) andLeAPL1(0.28). In Hoagland’s medium, the coefficients ofLeAPL3(0.83) andLeAPL2(0.62) were higher thanLeAPS(0.18) andLeAPL1(−0.62). This suggested different levels of contributions of these genes in starch biosynthesis in both media.