Expression of a novel bi-directional Brassica napus promoter in soybean

Protein profiling of fast neutron soybean mutant seeds reveals differential accumulation of seed and iron storage proteins

A fast neutron (FN) radiated mutant soybean (Glycine max (L.) Merr., Fabaceae) displaying large duplications exhibited an increase in total seed protein content. A tandem mass tag (TMT) based protein profiling of matured seeds resulted in the identification of 4338 proteins. Gene duplication resulted in a significant increase in several seed storage proteins and protease inhibitors. Among the storage proteins, basic 7 S globulin, glycinin G4, and beta-conglycinin showed higher abundance in matured FN mutant seeds in addition to protease inhibitors. A significantly higher abundance of L-ascorbate peroxidases, acid phosphatases, and iron storage proteins was also observed. A higher amount of albumin, sucrose synthase, iron storage, and ascorbate family proteins in the mutant seeds was observed at the mid-stage of seed filling. We anticipate that the duplicated genes might have a cascading effect on the genome constituents, thus, resulting in increased storage and iron-containing protein content in the mutant seeds.

Isolation and Functional Characterization of a Green-Tissue Promoter in Japonica Rice (Oryza sativa subsp. Japonica)

Simple Summary

Transgenic applications have largely focused on constitutive promoters in plants. However, strong and continuous over-expression of certain genes may be redundant and even harmful to plant growth. Thus, tissue-specific promoters are the most suitable for regulating target gene expression. Although several tissue-specific promoters have been identified, the regulatory mechanism of tissue-specific gene expression remains unclear. By a series of GUS staining of 5′ and 3′ deletions, we uncover tissue-specific cis-acting elements in GSX7R, including ten light-responsive elements. The results reveal that GSX7R is a reverse green tissue-specific promoter, except in endosperm. In contrast, strong tissue-specific promoters that can be used for rice improvements are limited. In this study, we successfully showed that the GSX7R promoter can drive the Cry1Ab gene to resistant rice yellow stem borer. In addition, our study demonstrates an effective promoter to drive foreign genes for crop improvement.

Abstract

Plant promoters play a vital role in the initiation and regulation of gene transcription. In this study, a rice protein/gene of unknown expression, named Os8GSX7, was gained from a rice T-DNA capture line. The semi-quantitative RT-PCR analysis showed that the gene was only expressed in root, glume, and flower, but not in stem, leaf, embryo, and endosperm of japonica rice. The GUS activity analysis of the GSX7R promoter showed that it was a reverse green tissue expression promoter, except in endosperm. The forward promoter of GSX7 cannot normally drive the expression of the foreign GUS gene, while the reverse promoter of GSX7 is a green tissue-specific expression promoter, which can drive the expression of the foreign GUS gene. The region from −2097 to −1543 bp was the key region for controlling the green tissue-specific expression. The regulatory sequences with different lengths from the 2097 bp reverse sequence from the upstream region of the Os8GSX7 were fused with the GUS reporter gene and stably expressed in rice. Furthermore, transgenic rice plants carrying Cry1Ab encoding Bacillus thuringiensis endotoxin, regulated by GSX7R, were resistant to yellow stem borer. The analysis suggested that 10 light responsive elements of tissue-specific expression were found, including ACE, Box4, CAT-box, G-Box, G-box, GATA motif, GC motif, I-box, Sp1, and chs-unit1 M1. In addition, the results of 5′ and 3′ deletions further speculated that ACE and I-box may be the key elements for determining the green tissue-specific expression of GSX7R promoter.

Proteomic Profiling of Fast Neutron-Induced Soybean Mutant Unveiled Pathways Associated with Increased Seed Protein Content

Mutagenesis through fast neutron (FN) radiation of soybean resulted in a mutant with a 15% increase in seed protein content. A comparative genomic hybridization analysis confirmed that the mutant is lacking 24 genes located at chromosomes 5 and 10. A tandem mass tag-based proteomic profiling of the wild type and the FN mutant revealed 3,502 proteins, of which 206 proteins exhibited increased abundance and 214 proteins showed decreased abundance. Among the abundant proteins, basic 7S globulin increased fourfold, followed by vacuolar-sorting receptor and protein transporters. The differentially expressed proteins were mapped on the global metabolic pathways. It was observed that there was an enrichment of 29 ribosomal proteins, 16 endoplasmic reticular proteins, and several proteins in export metabolic pathways. The deletion of the sequence-specific DNA binding transcription factor along with 23 other genes may have altered the negative regulation of protein syntheses processes, resulting in an increase in the overall protein content of the mutant seed. This mutant is a valuable resource for researchers to understand the metabolic pathways that may affect an increase in seed protein content (the mass spectrometry data files were submitted to massive.ucsd.edu # MassIVE MSV000084228).

Genomic changes and biochemical alterations of seed protein and oil content in a subset of fast neutron induced soybean mutants

BACKGROUND

Soybean is subjected to genetic manipulation by breeding, mutation, and transgenic approaches to produce value-added quality traits. Among those genetic approaches, mutagenesis through fast neutrons radiation is intriguing because it yields a variety of mutations, including single/multiple gene deletions and/or duplications. Characterizing the seed composition of the fast neutron mutants and its relationship with gene mutation is useful towards understanding oil and protein traits in soybean.

RESULTS

From a large population of fast neutron mutagenized plants, we selected ten mutants based on a screening of total oil and protein content using near infra-red spectroscopy. These ten mutants were regrown, and the seeds were analyzed for oil by GC-MS, protein profiling by SDS-PAGE and gene mapping by comparative genomic hybridization. The mutant 2R29C14Cladecr233cMN15 (nicknamed in this study as L10) showed higher protein and lower oil content compared to the wild type, followed by three other lines (nicknamed in this study as L03, L05, and L06). We characterized the fatty acid methyl esters profile of the trans-esterified oil and found the presence of five major fatty acids (palmitic, stearic, oleic, linoleic, and linolenic acids) at varying proportions among the mutants. Protein profile using SDS-PAGE of the ten mutants did exhibit discernable variation between storage (glycinin and β-conglycinin) and anti-nutritional factor (trypsin inhibitor) proteins. In addition, we physically mapped the position of the gene deletions or duplications in each mutant using comparative genomic hybridization.

CONCLUSION

Characterization of oil and protein profile in soybean fast neutron mutants will assist scientist and breeders to develop new value-added soybeans with improved protein and oil quality traits.

An event of alternative splicing affects the expression of two BnCYCD3-1-like genes in Brassica napus

Two full-length cDNAs of the cyclin-D3-1-like gene, named as BnCYCD3-1-like-1 and BnCYCD3-1-like-2 respectively were obtained from Brassica napus, both of which encoded a cell cycle protein CYCD3. Alternative splicing (AS) events of the two genes' transcripts were identified, assigned as BnCYCD3-1-like-1-1, BnCYCD3-1-like-1-2, BnCYCD3-1-like-2-1 and BnCYCD3-1-like-2-2 respectively. BnCYCD3-1-like-1-1 and BnCYCD3-1-like-2-1 were both fully-spliced transcripts which encoded a complete protein containing a LXCXE motif, two cyclin boxes and a PEST domain, while other two alternative splicing transcripts both resulted in the early termination of the protein translation. BnCYCD3-1-like-2-2 retained the third intron, lacking a PEST domain, while BnCYCD3-1-like-1-2 retained all the introns, lacking the C-terminal cyclin domain and a PEST domain. The expression pattern for tissue and development specification of the AS transcripts were investigated. The results showed that the standard splicing transcripts (BnCYCD3-1-like-1-1 and BnCYCD3-1-like-2-1) with complete structural domains were found with the most abundant expression in seeds, followed by leaves, and the least expression in stems. Both of BnCYCD3-1-like-2-1 and BnCYCD3-1-like-2-2 had the highest abundance in leaves, followed by roots. In addition, by applying various biotic and abiotic stresses on Brassica napus, the variations in the expression of each transcript under stress treatment were studied. Also, it was found that AS of the cyclin-D3-1-like gene may play an important role in helping Brassica napus respond to environmental stresses by coordinating the levels of transcripts of standard splicing and alternative splicing.