Alleviation of calcium toxicity in Arabidopsis thaliana by overexpressing GmHsp90s from soybean

In agriculture, supplemental calcium was applied to alleviate plant growth and development inhibition causing by various stresses. However, calcium overload is toxic to plants, which may prevent the germination of seeds and reduce plant growth rates. Hsp90 is an important molecular chaperone distributing in all living organisms and a series of studies have shown that Hsp90 and Ca²+ have closely relationship. To better understanding the relationship between GmHsp90s and calcium stress, we conducted a series of experiments and reported in this research article.

The study was performed by three techniques: 1) Quantitative RT-PCR with five GmHsp90 genes viz., GmHsp90A2, GmHsp90A4, GmHsp90B1, GmHsp90C1.1 and GmHsp90C2.1, 2) MDA, O₂- and chlorophyll content assay of transgenic plants after calcium stress and 3) Phenotype analysis of transgenic plants in pod setting period after three days treatment of water or 80 mM CaCl₂.

Quantitative RT-PCR with the five genes showed that they were all CaCl₂ inducible. MDA, O^2- and chlorophyll content assay showed that GmHsp90A2 and GmHsp90A4 transgenic lines significantly relieved the damage caused by CaCl₂ and oxidative stress. The secondary stress damage, including the effect on plant height and pod setting rate, was also reduced in transgenic lines, especially GmHsp90B1 and GmHsp90C1.1 transgenic lines. Collectively, this study reveals the response of GmHsp90s to calcium and their potential function in coping with calcium stress.