Transcriptional rearrangement by plant growth-promoting rhizobacteria in priming drought tolerance in plants
Type of DegreeMaster's Thesis
Entomology and Plant Pathology
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In recent decades, the scarcity of water, referred to as drought, has become one of the most main problems in agriculture throughout the world. Especially since recent increases in human population, and the global climate change, an urgent need has been emerged to develop novel, effective and sustainable strategies such as generating new crop cultivars that confer tolerance or resistance towards drought. Thus, as an initial step, this study aims to uncover generic principles in the heightened states of drought tolerance (or resistance) in Arabidopsis by i) establishing plant growth-promoting rhizobacteria (PGPR) as biostimulants for priming drought tolerance (or resistance), ii) determinng the pattern change of PGPR-responsive transcripts, and iii) discerning genes directely associated with drought tolerance (or resistance) from a list of genes, associated with plant growth and/or responsive to drought and other environmental stresses. Here our new qualitative and high-throughput quantitative analyses both agreed that selective PGPR strains in the species of Panebacillus polymyxa and Bacillus amyloliquefaciens can prime drought tolerance in Arabidopsis, and soybean plants. The priming occurs in parallel to the rapid induction of PGPR-inducible genes (PIGs) which are associated with abscisic acid (ABA) and jasmonic acid (JA) signaling pathways. Interestingly, a subset of ABA-dependent PIGs are known as ‘memory’ genes in dehydration, suggesting that PGPR hijack and trigger drought-induced systemic resistance (ISR). However, PIGs also include other ABA-responsive genes that are induced by drought and other abiotic stresses such as cold temperature (i.e., Low temperature induced 79, also called RD29A, gene) but reported as non- memory gene. Hence, we conclude that an intricate metabolic network is involved in the PGPR-induced priming of drought tolerance which also related to other stress acclimation processes (e.g., cold, tissue injury and UV damage) as well as disease resistance (e.g., microbial and insect infections), which are agreed with the known benefactory effects of PGPR towards various aspects of plant growth, development and survival.