An embryo lethal transgenic line manifests global expression changes and elevated protein/oil ratios in heterozygous soybean plants

Abstract

Understanding the molecular processes of seed development is important especially in agronomic crops that produce large amounts of nutrient reserves. Because soybean is a vital source of vegetable protein worldwide, producers are concerned about increasing the total amount of protein in the seed without substantially lowering the amount of oil, another economically important product. Here we describe a transgenic soybean line with increased protein and protein/oil ratio, containing an average of 42.2% protein vs. 38.5% in controls and with a protein/oil ratio of 2.02 vs. 1.76 in controls over several generations of greenhouse growth. Other phenotypic data show that the seeds are heavier, although there are overall lower yields per plant. We postulate these effects result from insertion site mutagenesis by the transgenic construct. As this line never achieves homozygosity and appears to be embryo lethal when homozygous, one functional copy of the gene is most likely essential for normal seed development. Global transcript analyses using RNA-Seq for 88,000 gene models over two stages of cotyledon development revealed that more genes are overexpressed in the transgenic line including ribosomal protein related genes and those in the membrane protein and transporters families. Localization of the insertion site should reveal the genes and developmental program that has been perturbed by the transgenic construct, resulting in this economically interesting increase in protein and the protein/oil ratio.

Genome-wide Association Study for Yield and Yield-Related Traits in Diverse Blackgram Panel (Vigna mungo L. Hepper) Reveals Novel Putative Alleles for Future Breeding Programs

“…For seeds per pod, galactinol synthase two in Chickpea ( Salvi et al, 2016 ), Golgi apparatus membrane enzyme-like enzyme ECHIDNA in Arabidopsis ( Jia et al, 2018 ), 60S ribosomal protein L28-2 in soybean ( Jones et al, 2020 ), dihydrofolate synthetase in Arabidopsis ( Corral et al, 2018 ), and ethylene-responsive transcription factor 1B-like enzyme in brassica ( Kaur et al, 2020 ) were known to have a role in increasing number of seeds per pod/siliqua. For yield per plant, myb-related protein 305-like in Arabidopsis ( Ambawat et al, 2013 ), CLAVATA3/ESR (CLE)-related protein 5-like in Arabidopsis ( Fletcher, 2018 ), transcription factor PCF5 in wheat ( Zhao et al, 2018 ), sodium/calcium exchanger NCL in soybean ( Liu Y. et al, 2016 ), basic leucine zipper 34 isoform X1 enzymes in wheat ( Sornaraj et al, 2016 ), alpha-mannosidase-like in wheat ( Dal Cortivo et al, 2020 ), and putative 12-oxophytodienoate reductase 11 in wheat ( Pigolev et al, 2018 ) were previously known for yield improvement.…”

Progress in Soybean Genetic Transformation Over the Last Decade

“…Transgenic technology has been used to improve soybean agronomic traits, which include yield component, grain quality, and biotic and abiotic stress tolerance, and economic traits such as oil and biofuel quality, and specific chemical content in seed for human health, and other traits. Trait improvements through forward and reverse genetic approaches in the last 5 years are summarized in Table 2; i.e., downregulation of the pyruvate dehydrogenase kinase gene GmPDHK through RNAi made an average of 42.2% protein content in seeds of transgenic plants, which is significantly increased compared with the non-transgenic control (Jones et al, 2020). Soybean seeds with linolenic acid content in excess of 50% of the total oil have been generated by increasing the expression of the FAD3 gene, which encodes the enzyme that converts linoleic acid to linolenic acid (Yeom et al, 2020).…”