For proline content, rosette leaf samples were taken simultaneous with other physiological traits tests. (a) Proline content of Arabidopsis plants, (b) Relative expressions of AtP5CS1 in Arabidopsis plants. Error bars indicate SD; n = 3; and leaves were prepared from at least five independent plants for each repeat. For quantitative real-time PCR analyses, Arabidopsis plants were grown in normal conditions and rosette leaf samples were collected from three-week-old plants. An Arabidopsis actin gene was used as internal control for normalization. The relative mRNA level for each gene was calculated as ΔΔCT values. The result of expression was generated by SigmaPlot 9.0. The transcript levels (means ± SD) displayed were each calculated using the qRT-PCR results of three technical repeats. Leaves of each repeat were prepared from at least five independent plants. Control, vector control plants; A2, A4, B1, C1.1, C2.1 represent the GmHsp90A2, GmHsp90A4, GmHsp90B1, GmHsp90C1.1 and GmHsp90C2.1 transgenic lines, respectively.