Morphological and cytosine DNA methylation changes induced by a combined effect of boron (B) and salt toxicity in Sorghum bicolor inbred line

Abstract

Boron (B) toxicity is one of the abiotic stresses limiting plant growth in arid and semi arid regions globally. Although studies have been conducted on the combined effect of B and sodium chloride (NaCl) toxicity on overall plant growth revealing an antagonistic relationship, the morphology and epigenetic interactions have not fully been explained. Germinating seeds of an inbred line of Sorghum bicolor (YN267) were subjected to various concentrations of B (10, 50, 100, 200, 300 and 400 mM) in a constant concentration of high NaCl (100 mM). Methylation-sensitive amplification polymorphism (MSAP) was used in the assessment of changes in the methylation levels and patterns. Morphological results show that plants at the B concentration range of 10 to 200 mM were adversely affected by the combined stress application than at 300 and 400 mM. In addition, the cytosine methylation status at 300 mM showed an increased overall hypermethylation, while hypomethylation was induced at 400 mM. These results show that not only did the combined treatment induced cytosine DNA methylation changes which was reflected in the plant morphology, but the alleviating effects of the combination at toxic levels are suggested to be due to the epigenetic alterations and expression/repression of stress responsive genes.