7. Conclusion and future prospects
Flooding and drought stresses exert deleterious effects on soybean growth [25]. Considering the importance of soybean, clarification of the underlying mechanisms in response to combined stresses is absolutely needed. Organ-specific analysis indicated that root tip in the early-stage soybean was more sensitive to both stresses than other organs. Protein quality control and calcium homeostasis were disrupted in the ER of soybean exposed to combined stresses. Furthermore, increased-cytosolic calcium in stressed soybean was verified from the ER and it further induced the accumulation of pyruvate decarboxylase. These findings employing proteomic studies suggest that calcium homeostasis might represent the bridge between cytosol and subcellular compartment in plant cell of soybean-root tip in response to combined stresses. In addition, calcium release from the ER was required for unfolded protein response [104] and elevated cytosolic calcium directed pyruvate in stressed soybean [32], indicating the importance of calcium roles on protein metabolism and energy regulation to cope with flooding and drought stresses.
On the other hand, decreased-ribosomal proteins were responsible for suppressed-protein synthesis; however, heterogeneity in ribosomal proteins displayed different selectivity for translating sub-pools of transcripts in mammalian cell [156]. This sheds light on ribosome specificity in plant in response to stresses. Stress-dependent response was compared between flooding and drought; however, upstream events such as stress sensing and transduction are limited, suggesting that concerns might be placed on emphasis. Overall, elucidation of stress-response processes based on integrated datasets of “-omics”, clarification of responsive pathways from stress sensing to plant adaptation, and validation of protein function in vivo will aid in developing stress-tolerant soybean in the future.
