Transcriptional analysis reveals induction of systemic resistance in tomato treated with Chlorella microalgae

Abstract

The application of algae-based products has been reported to promote plant growth and yield of tomato plants, especially by enhancing flowering. However, how microalgae (MA) affect plants at the molecular level remains elusive. The aim of this study was to elucidate the effects of live microalgae application on plant photosynthesis and the transcriptome of the unopened flower buds of tomato plants. Microalgae increased leaf temperature differential in tomato leaves but hardly affected photosynthesis. Contrary to our expectations, RNA-seq data revealed remarkable differential expression of several genes participating in responses to abiotic stresses but only a few genes involved in flowering or pollen/ spore development. Late Embryogenesis Abundant (LEA) proteins (mostly dehydrins), oleosins, ethylene, and abscisic-related genes, and Nascent Polypeptide-Associated Complex (NAC)-domain-containing proteins were upregulated. Genes involved in carbohydrate metabolism were also differentially expressed, glycolysis-related genes were upregulated, while those involved in sugar transport were downregulated. The only upregulated gene implicated in the induction of flowering was Solyc07g006500.3.1 (encoding trehalose-6-phosphate synthase enzyme TPS1). Overall, microalgae treatment led to an empirical upregulation of genes involved in jasmonic acid, abscisic acid, and ethylene pathways which are all essential for abiotic stress response. This study shows that microalgae treatment primed plants by inducing the expression of genes involved in response to abiotic stress, especially cold and water stress, as well as pathogen attack.