Disruption in Jasmonic Acid Biosynthesis Influences Metabolism of Other Hormones in Arabidopsis

Hormones are the key mediators of plant growth, development, and adaptive responses to diverse environmental growth conditions. However, the knowledge of how the endogenous concentration of a hormone affects those of other hormones in plants during their growth is not completely comprehended. JA (jasmonic acid) is a key hormone having multifaceted roles in shaping plant growth and development and driving plant responses to abiotic and biotic stressors. Here, we studied how the disruption in the JA biosynthetic pathway in Arabidopsis thaliana affects the homeostasis of other hormones by measuring the concentrations of various hormones, including ABA (abscisic acid), AUX [auxin, specifically IAA (indole-3-acetic acid)], CKs (cytokinins), GAs (gibberellins), and SA (salicylic acid) in 10 days old Arabidopsis JA-deficient aos (allene oxide synthase) knock-out mutant seedlings. We noted increased levels of trans-zeatin class of CKs but reduced levels of cis-zeatin and isopentenyladenine class of CKs, as well as reduced levels of IAA, GAs, and SA in the aos mutant seedlings, compared with WT (wild-type) seedlings. We also noted reduced expression levels of the genes associated with AUX biosynthesis but increased expression levels of the genes associated with the catabolism of SA and GAs in aos mutant plants compared with those of corresponding genes in WT plants. These results indicate that the levels of these hormones are positively correlated with that of JA in plants during their growth, at least at the seedling stage.