Determination of cadmium and/or drought stress effects on some plant phytohormone contents and hormone gene expressions in bean (Phaseolus vulgaris L)

Abstract

Plants can sometimes be under the influence of more than one stress factor. In this case, combined stress factors can cause different responses in plants. In this study, the phytohormonal activity and hormone gene expressions of beans (Phaseolus vulgaris L.) were investigated in different drought levels and soils with different levels of cadmium accumulation. Plants were grown at 4 different cadmium (Cd) levels (Cd: 0, Cd1: 100, Cd2: 150, and Cd3: 200 mg kg$^{-1}$) and 3 irrigation levels (D0: 100%, D1: 75%, and D2: 50% of field capacity). Abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid (GA), salicylic acid (SA), cytokinin, zeatin, and jasmonic acid contents and gene expressions related to them were investigated. As a result of the study, we determined that there was a significant decrease in the content of IAA, GA, SA, cytokinin, zeatin, and jasmonic acid with increasing doses of drought and Cd. Especially with the coexistence of both stress factors, this reducing effect (the reductions in these hormones were 86.6%, 64.1%, 71.9%, 66.7%, 45.5%, and 73.9% as compared to D0, respectively) on the measured parameters was greater. However, ABA content increased significantly with drought and/or Cd stresses, especially with Cd3D2, about a thousand times higher than the control. On the other hand, mRNA transcript levels of some hormone genes (ABA 8'-hydroxylase, adenylate isopentenyltransferase (AIPT3), auxin-related protein (AUX/ IAA), MeJA biosynthesis and gibberellin 20-oxidase and NRAMP2 gene known to be involved in Cd transport, were detected. According to the results, while ABA 8'-hydroxylase, gibberellin 20-oxidase, and NRAMP2 genes were overexpressed in all stress treatments, AIPT3 and AUX/IAA genes were down-regulated and also, MeJA biosynthesis gene varied depending on dose and stress.