A sucrose binding protein and ß-conglycinins regulate soybean seed protein content and control multiple seed traits

Authors: LAKHSSASSI, NAOUFAL - Southern Illinois University; EL BAZE, ABDELHALIM - Southern Illinois University; BADAD, OUSSAMA - Southern Illinois University; ZHOU, ZHOU - Southern Illinois University; MALLORY, CULLEN - Southern Illinois University; KNIZIA, DOUNYA - Southern Illinois University; MEKSEM, JONAS - Duke University; LAKHSSASSI, AICHA - Université Abdelmalek Essaâdi; VUONG, TRI - University Of Missouri; Bellaloui, Nacer; NGUYEN, HENRY - University Of Missouri; MEKSEM, KHALID - Southern Illinois University

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soybean is a complete and a major source of plant protein with several benefits for human and animals. The protein ingredients market is driven by several factors including protein functionalities, healthy diet, nutritional value, and healthcare products. The availability of high protein soybean varieties is indeed crucial for the soybean meal industry. A few soybean varieties with high protein content have been identified during the last decade. However, it has been observed that most of the developed soybeans with high protein content were affected in their oil composition and presented non-stable protein content. Thus, improving soybean protein content and amino acid composition has been a long-term goal of many research studies worldwide. The glycoprotein beta-Conglycinin is a primary class of seed storage proteins made of a three subunits alpha prime, alpha, and beta, and constitute about 35% of the seed total protein. The objective of this research was to develop a unique strategy to modify the protein content and composition of soybean seeds by targeting the beta-ConGlycinin subunits. Using Targeting Induced Local Lesions In Genomes (TILLING)-by-Sequencing+ technology, several mutants within the four major beta-ConGlycinin gene family members were isolated. We were able to characterize five GmCoGy1, two GmCoGy2, three GmCoGy3, and four GmCoGy4 mutants. Interestingly, all obtained mutants from the GmCoGy1, GmCoGy2, and GmCoGy4 genes showed a significant increase in their protein content (up to 26%) when compared to the control Forrest “wild-type”. Several beta-ConGlycinin mutants with high protein content also showed a stable and/or increase in their total oil levels, in addition to a significant changes to their seed amino acid composition. This research demonstrated that the use of TILLING-by-Sequencing+ technology provides a great alternative technique to understand the role of the protein storage in soybean by controlling seed protein content and amino acid composition. The developed beta-ConGlycinin lines in the current study will benefit soybean farmers, private industry, and breeders for developing soybean lines with high protein content while maintaining their oil content.

Technical Abstract: Soybean is a complete and a major source of plant protein with several benefits for human and animals. The protein ingredients market is driven by several factors including protein functionalities, healthy diet, nutritional value, and healthcare products. The availability of high protein soybean varieties is indeed crucial for the soybean meal industry. A few soybean varieties with high protein content have been identified during the last decade. However, it has been observed that most of the developed soybeans with high protein content were affected in their oil composition and presented non-stable protein content. Thus, improving soybean protein content and amino acid composition has been a long-term goal of many research studies worldwide. The glycoprotein ß-Conglycinin is a primary class of seed storage proteins made of a trimer which consists of three subunits a’, a, andßand constitute about 35% of the seed total protein. The objective of this research was to develop a unique strategy to modify the protein content and composition of soybean seeds by targeting the ß-ConGlycinin subunits. Using Targeting Induced Local Lesions In Genomes (TILLING)-by-Sequencing+, several mutants within the four major ß-ConGlycinin gene family members were isolated. We were able to characterize five GmCoGy1, two GmCoGy2, three GmCoGy3, and four GmCoGy4 mutants carrying missense or nonsense mutations. Interestingly, all obtained mutants from the GmCoGy1, GmCoGy2, and GmCoGy4 genes showed a significant increase in their protein content (up to 26%) when compared to the control Forrest-WT. Several ß-ConGlycinin mutants with high protein content also showed a stable and/or increase in their total oil levels, in addition to a significant changes to their seed amino acid composition. Using 2D-PAGE analysis, we were able to confirm the changes to the soybean seed protein profile. The finding supports the observed changes in amino acid composition. The results showed the possibility of redirecting the carbon flux toward oil, glycinins, and amino acid biosynthesis when decreasing the amount of soybean seed ß-ConGlycinins by EMS mutagenesis. This research demonstrated that the use of reverse genetic approach like TILLING-by-Sequencing+ provides a great alternative technique to understand the role of the protein storage in soybean by controlling seed protein content and amino acid composition. The developed ß-ConGlycinin lines in the current study will benefit soybean farmers, private industry, and breeders for developing soybean lines with high protein content while maintaining their oil content.