Proteomic responses of maize roots to the combined stress of sulphur deficiency and chromium toxicity

Abstract

Sulphur (S) metabolism plays a crucial role in response to heavy metal stress. It has been well demonstrated that the deficiency of S is a limiting factor to plant capability to cope with chromium (Cr) stress. However, little is known about the plant response to S-deficiency and Cr stress at the proteome level. In the present study, a hydroponic experiment was conducted to examine the role of S supply on Cr-induced proteomic alterations in the roots of maize seedlings. Maize seedlings were exposed to Cr (0 and 100 μM) and different S concentrations (0 and 1 mM) for seven days. Biomass accumulation (fresh and dry weights) was significantly decreased by Cr stress (100 μM), and this decrease was more pronounced under S-deficiency condition. Analysis of proteins on gels detected 54 proteins that exhibited differential expression patterns, out of which 38 were identified by matrix-assisted laser desorption ionization time-of-flight/ time-of-flight (MALDI-TOF/TOF) mass spectrometry. Of these, 21 proteins were up-regulated and 17 proteins were down-regulated by >1.5-fold S-deficiency and/or under Cr stress. The majority of the proteins functioned in stress defence, protein metabolism, and energy metabolism. Our results show that S supplementation enhanced the tolerance to Cr stress by increasing the abundance of stress defence-related proteins including pathogenesis-related protein 10, glutathione peroxidase, superoxide dismutase [Mn], glutathione S-transferase 3, proteasome subunit alpha type 6, IN2–1 protein, and ABA-responsive protein. This study may provide new insights into the proteomic response mechanisms of maize seedlings under Cr stress and/or S-deficiency.