Coordinate transcriptional activation of salicylic acid and trehalose synthesis, oxidative/ER stress and innate immunity pathways by inducible artificial microRNA silencing of the SNF4 activator subunit of Arabidopsis SnRK1. Arabidopsis thaliana

Arabidopsis SnRK1 is structurally and functionally related to the yeast Snf1 and mammalian AMP-activated kinases, which are activated in response to carbon/glucose limitation and stress conditions causing an imbalance of energy homeostasis increasing the AMP/ATP ratio. Mutations of the SNF4 activating subunit of trimeric Arabidopsis SnRK1 complexes are not transmitted through the male meiosis. Silencing of SNF4 by a β-estradiol-inducible artificial microRNA (amiR-SNF4) constructs was used to examine how inhibition of SnRK1 affects transcriptional regulation of different cellular pathways in dark and light grown seedlings. This study shows that amiR-SNF4 silencing of SnRK1 leads to coordinate transcriptional activation of salicylic acid and trehalose synthesis, oxidative/endoplasmic reticulum stress and pathogen defense responses by inducing simultaneous changes in numerous other essential hormonal and metabolic pathways in Arabidopsis. We used Affymetrix ATH1-121501 Genome Array to compare global transcript levels in wild type and β-estradiol-induced amiR-SNF4 mutant seedlings 5 days after germination in the dark or light. Overall design: Wild type and amiR-SNF4 mutant Arabidopsis (Col-0) seedlings were grown in either darkness or light (22°C, 400 μEinstein m−2s−1 irradiance, 8h light/16 dark) in the presence 5 µM β-estradiol on 0.5 MS medium containing 0.5% sucrose and ½ concentration of macro elements. (Koncz, C., Martini, N., Szabados, L., Hrouda, M., Bachmair, A., and Schell, J. (1994). Specialized vectors for gene tagging and expression studies. In: Plant Molecular Biology Manual, Gelvin,S., and Schilperoort, B. (eds.), Kluwer Academic Publishers, Dordrecht-Boston-London, B2, 1-22.) Seedling were collected at 4h after the start of the light period in liquid nitrogen for RNA preparation. At this stage, trypan-blue staining detected no visible signs of cell death in amiR-SNF4 seedlings. Steady-state mRNA levels in total RNA samples of 5 days old seedlings dark and light grown were compared.