Soybean mutants lacking abundant seed storage proteins are impaired in mobilization of storage reserves and germination

Authors: WEI, XIAOSHUANG - Northeast Agricultural University, China; KIM, WON-SEOK - University Of Missouri; SONG, BO - Northeast Agricultural University, China; Oehrle, Nathan; LIU, SHANSHAN - Northeast Agricultural University, China; Krishnan, Hari

Submitted to: ACS Omega
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2020
Publication Date: 3/31/2020
Citation: Wei, X., Kim, W., Song, B., Oehrle, N.W., Liu, S., Krishnan, H.B. 2020. Soybean mutants lacking abundant seed storage proteins are impaired in mobilization of storage reserves and germination. ACS Omega. 5(14):8065-8075. https://doi.org/10.1021/acsomega.0c00128.
DOI: https://doi.org/10.1021/acsomega.0c00128

Interpretive Summary: The major storage reserves of soybean, protein and oil, are mobilized during germination and seedling growth. These storage reserves provide the necessary energy and metabolic intermediates needed for the growth of seedling. Previously, it was reported that seed storage mutants can grow and reproduce normally without any apparent physiological abnormalities in spite of loss of seed proteins. In this study, we evaluated a soybean line (BSH-2) that lacks several abundant seed storage proteins to systematically examine if the loss of seed proteins have any influence on the seed germination efficiency and post-germinative seedling establishment. Our biochemical and ultrastructural study demonstrated the soybean seed storage mutants were affected in mobilization of seed reserves and had low seed germination efficiency. Uniform germination is critical since uniform emergence leads to uniform plants and ultimately high yield potential. The information obtained from this study will eventually benefit the US soybean farmers in enabling them to obtain uniform seed germination in the field via a better understanding of seed storage proteins.

Technical Abstract: Spontaneous and radiation-induced mutants of soybean, despite loss of abundant seed proteins, have been reported to grow and reproduce normally without any apparent physiological abnormalities. Here, we report the development and characterization of a soybean line (BSH-2) that lacks several abundant seed storage proteins. One dimensional and high-resolution two-dimensional gel electrophoresis revealed the absence of the a' and a subunits of ß-conglycinin and G1, G2, G4, and G5 glycinin in the newly developed mutant line (BSH-2). Like our earlier developed soybean mutant line (BSH-3), the seeds of BSH-2 also accumulated high levels of free amino acids as compared with wild-type DN47 seeds. An examination of the germination rates revealed that both BSH-2 and BSH-3 had significantly lower germination rates compared with the parent line DN47. Two-dimensional gel electrophoresis analysis demonstrated that these mutants had slower rates of mobilization of seed storage proteins. The delayed mobilization of storage proteins in BSH-2 and BSH-3 seeds was also correlated with a delayed induction of proteolytic activity in the mutants when compared to DN47. Similarly, qRT-PCR analysis revealed distinct expression pattern of genes involved in proteolytic pathway in the mutants when compared to DN47. Transmission electron microscopy observation of soybean seeds at two germination stages revealed striking differences in the breakdown of protein storage vacuoles and lipid bodies in the mutants. Our study demonstrates that BSH-2 and BSH-3 are compromised in mobilization of storage reserves and the absence of abundant storage proteins may affect the seed germination efficiency and post-germinative seedling establishment.