Effect of Drought Stress on Soybean Nodule Proteomes and Expression of Cysteine Proteases

Soybean is a valuable crop cultivated as an excellent source of proteins, dietary fibre, and a variety of micronutrients. Rhizobia reside as symbiosomes in the infected cells of soybean nodules to fix atmospheric nitrogen. Such association ensures optimal yield and may be beneficial in quenching the use of fertilizers. However, premature nodule senescence remains one of the major problems affecting soybean growth and yield. A clear understanding of the molecular level on the resultant effects of factors that promote early nodule senescence is important. Cysteine proteases are the proteases directly involved in the commencement of early tissue senescence. Nevertheless, the studies performed on the involvement of these proteases in nodule senescence have not reached a consensus. Besides, the specific family and isoforms of cysteine proteases expressed under normal well-watered, waterlogging and water deficit conditions during nodule senescence are not clearly understood. Consequently, there is a need for conducting intensive molecular studies on the involvement of cysteine proteases in nodule senescence. Changes in the whole proteome of a healthy and a senescing nodule need to be understood to make conclusive findings on the molecular events that occur during senescence. The use of proteomic approaches to investigate the level and characteristics of the proteins in general, by preparing a protein map and its application to functional analysis in soybean nodule senescence is important in delaying premature senescence.

Keywords: Cysteine proteases, Cystatins, Drought stress, Nodule senescence, Proteomics, Rhizobia, Soybean.