Comparative Proteomic Analysis of the Hevea brasiliensis Latex under Ethylene and Calcium Stimulation

Calcium ions usually act as a second messenger in the signal transmission process and a major element required by plants. In Hevea, calcium ion could alleviate the negative effects of long-term ethylene application to a certain extent. However, the molecular mechanisms remain unclear.

Two-dimensional electrophoresis was used to determine the pattern of protein changes in latex after treatments with calcium and/or ethylene. Quantitative real-time polymerase chain reaction and Western blotting were used to determine the expression levels of some proteins and genes. STRING software was used to determine the protein-protein interaction network of the identified proteins.

Comparative proteomics identified 145 differentially expressed proteins, which represented 103 unique proteins. The abundance change patterns of some proteins involved in signal transduction, rubber particle aggregation, and natural rubber biosynthesis were altered upon calcium stimulation. Quantitative real-time polymerase chain reaction analysis of 29 proteins showed that gene expression did not always maintain the same trend as protein expression. The increased enzyme activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase suggested that calcium can enhance the antistress ability of plants by increasing the activity of their antioxidant enzyme systems.

These results supplement the rubber latex proteome, and provide evidence for investigating the molecular mechanisms by which calcium alleviates the negative effects of ethylene stimulation.