Cadmium Hyperaccumulation Mechanism of Solanum Nigrum L. With Exploration from the Perspective of Differential Protein Expression Based on Itraq Proteomics Compared to its Zinc Accumulation Characteristic

Abstract

Solanum nigrum L. is a Cd hyperaccumulator, but non-hyperaccumulating Zn simultaneously, and the molecular mechanism is still unclear. Isobaric tags for relative and absolute quantitation (iTRAQ) was used to explore this phenomenon through the comparation of differential expression proteins (DEPs) characteristics of S. nigrum accumulating Cd and Zn. The results showed that biomasses of S. nigrum were not changed, and Cd translocation factor was higher than 1, but lower than 1 for Zn under hydroponic condition of 1 μM Cd or 31 μM Zn addition. The number of co-intersecting specific proteins of L1μMCd/ck/R1μMCd/ck (L, leaf; R, root) and L31μMZn/CK/R31μMZn/CK was only 6 among 718 L1μMCd/ck/R1μMCd/ck DEPs and 643 L31μMZn/ck/R31μMZn/ck DEPs, which might be part reasons of S. nigrum can simultaneous accumulation Cd and Zn, but hyperaccumulating Cd only. COG function and KEGG analysis showed that the key roles in protein expression regulation might involve in metabolic pathways including protein export, aminoacyl tRNA biosynthesis, phagosome, amino sugar and nucleoside sugar metabolism, protein processing in endoplasmic reticulum and ribosome. The results of some index of antioxidant and detoxification in S. nigrum indirectly affirmed these roles. The new found is important for exploring the hyperaccumulation mechanism.

Keywords: differential expression protein (DEP), isobaric tags for relative and absolute quantitation (iTRAQ), Solanum nigrum L., cadmium (Cd), zinc (Zn), Hyperaccumulation