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Soybean is the primary source of vegetable protein and is used for various purposes, mainly to feed animals. This crop can have diverse seed coat colors, varying from yellow, black, brown, and green to bicolor. Black seed coat cultivars have already been assigned as favorable for both seed and grain production. Thus, this work aimed to identify genes associated with soybean seed quality by comparing the transcriptomes of soybean seeds with contrasting seed coat colors. The results from RNA-seq analyses were validated with real-time PCR using the cultivar BRS 715A (black seed coat) and the cultivars BRS 413 RR and DM 6563 IPRO (yellow seed coat). We found 318 genes differentially expressed in all cultivars (freshly harvested seeds and seeds stored in cold chamber). From the in silico analysis of the transcriptomes, the following genes were selected and validated with RT-qPCR: ACS1, ACSF3, CYP90A1, CYP710A1, HCT, CBL, and SAHH. These genes are genes induced in the black seed coat cultivar and are part of pathways responsible for ethylene, lipid, brassinosteroid, lignin, and sulfur amino acid biosynthesis. The BRSMG 715A gene has almost 4times more lignin than the yellow seed coat cultivars. These attributes are related to the BRSMG 715A cultivar’s higher seed quality, which translates to more longevity and resistance to moisture and mechanical damage. Future silencing studies may evaluate the knockout of these genes to better understand the biology of soybean seeds with black seed coat.

The present study aimed to identify the relationship between lignin content in soybean pods, pod dehiscence rate, gene expression from phenylpropanoid pathway, cell wall lignification, and deterioration of seed due to weather. To evaluate the weathering deterioration, an experiment simulating 150 mm of rainfall was performed in greenhouse conditions. Gene expression was assessed by RT-qPCR. Results showed that soybean cultivars BRS Jiripoca and BRS 388 RR considered tolerant to weathering deterioration, presented higher levels of lignin content in pods. The data showed that dehiscence rate was neither a trait involved in weathering deterioration tolerance nor in lignin content in soybean pods. Lignin content and weathering deterioration were highly negatively correlated, probably due to changes in cell wall permeability to water accordingly to lignin level. Higher expression levels of genes involved in lignin biosynthesis and cell wall lignification were identified in both tolerant cultivars, however, with opposite expression profiles and in different developmental phases, suggesting a possible temporal strategy to cope with environmental adverse conditions.

Drought is one of the most stressful environmental factor causing yield and economic losses in many soybean-producing regions. In the last decades, transcription factors (TFs) are being used to develop genetically modified plants more tolerant to abiotic stresses. Dehydration responsive element binding (DREB) and ABA-responsive element-binding (AREB) TFs were introduced in soybean showing improved drought tolerance, under controlled conditions. However, these results may not be representative of the way in which plants behave over the entire season in the real field situation. Thus, the objectives of this study were to analyze agronomical traits and physiological parameters of (1Ab58), (1Bb2193), and (1Ea2939) GM lines under irrigated (IRR) and non-irrigated (NIRR) conditions in a field experiment, over two crop seasons and quantify transgene and drought-responsive genes expression. Results from season 2013/2014 revealed that line 1Ea2939 showed higher intrinsic water use and leaf area index. Lines 1Ab58 and 1Bb2193 showed a similar behavior to wild-type plants in relation to chlorophyll content. Oil and protein contents were not affected in transgenic lines in NIRR conditions. Lodging, due to plentiful rain, impaired yield from the 1Ea2939 line in IRR conditions. qPCR results confirmed the expression of the inserted TFs and drought-responsive endogenous genes. No differences were identified in the field experiment performed in crop season 2014/2015, probably due to the optimum rainfall volume during the cycle. These field screenings showed promising results for drought tolerance. However, additional studies are needed in further crop seasons and other sites to better characterize how these plants may outperform the WT under field water deficit.

The yield and protein content of soybean seeds are challenging traits for breeding since they have a negative correlation. To solve this issue, it is essential to understand the protein transport in soybean seeds. Here we performed an analysis of 3 datasets containing transcriptional data from soybean seeds and pods, without any treatment, aiming to select genes related to the transport of organic nitrogen compounds. We identified 69 transporters, and among them, seven were chosen to be validated by qRT-PCR. Seeds and pods of soybean cultivars BRS 232 and BRS 284, respectively, presenting higher and lower protein content, were assayed under normal growth condition. Results showed in BRS 232 soybean cultivar, a positive correlation between seed protein content and gene expression for five out of the seven genes analyzed. These nitrogen compounds transporters can play an essential role in the storage of proteins, thus increases the protein content of soybean seeds and contributes to the decrease the negative correlation between yield and protein content of soybean seeds.

Water deficit may occur at any stage of crop development, affecting productivity and causing economic losses. In response to drought, raffinose family oligosaccharides (RFOs) are accumulated in plant tissues stabilizing and protecting cell membranes and keeping the vital functions. The enzyme galactinol synthase (GolS, EC 2.4.1.123) catalyzes the first step in the biosynthesis of RFOs. In our study, soybean events overexpressing 35S:AtGolS2 were molecularly, physiological, and agronomical characterized, under drought simulated in greenhouse and in field conditions during the crop season 2014/2015. The conventional soybean cultivar BRS 184 was transformed and five positive events were obtained. Four events transmitted the transgene to further generations and in the events 2Ia1 and 2Ia4, two to four copies of AtGols2 gene were observed. Results in greenhouse showed that the overexpression of AtGolS2 in genetically modified (GM) plants led to increased galactinol transcripts, probably resulting in changes in carbohydrate metabolism. Accumulation of these transcripts that may have acted as osmoprotectors, lead to higher drought tolerance and survival rate of 2Ia4 plants. In addition, in field conditions, higher yield was observed for 2Ia4 plants under irrigated (IRR) and non-irrigated (NIRR) treatments. This result can be due to the increased synthesis of RFOs even under well-watered conditions. This field screening showed promising results for drought tolerance, suggesting that 2Ia4 plants may be useful in a breeding program for the development of drought-tolerant plants. However, additional studies are needed in further crop seasons and other sites to better characterize how these plants may outperform the WT plants under water deficit.

Spliceosome mediated intron removal from precursor mRNAs (pre-mRNAs) generates circular RNAs called intron lariats. RNA DEBRANCHING ENZYME 1 (DBR1) ribonucleases linearize, or debranch, intron lariats to allow their degradation. DBR1 genes occur across eukaryotes and are essential in animals and plants. High levels of intron lariats in the weak Arabidopsis thaliana dbr1-2 allele inhibits primary microRNA (pri-miRNA) processing, disrupting miRNA production and miRNA-regulated growth and development. Arabidopsis sickle (sic) mutants alter pri-miRNA processing and pre-mRNA splicing. This study demonstrates sic mutants accumulate intron lariats matching those in weak dbr alleles. The strong sic-1 and weak dbr1-3 alleles together cause synthetic lethality, while weak sic-3 with dbr1-3 has intron lariat accumulation like sic-3. Further, sic-3, dbr1-3, and sic-3 dbr1-3 similarly alter circadian rhythms and growth of roots and rosettes. The conserved MPLKIP amino acid motif in SIC mediates physical interaction with DBR1 in vitro and is required for intron lariat debranching in vivo. Thus, MPLKIP containing proteins, like SIC and human TTDN1, act with cognate DBR1 proteins to maintain RNA homeostasis critical for growth and development.

BackgroundThe drought condition is responsible for considerable losses in soybean production, which in turn may result in billionaire losses. After drought perception, plants activate a cascade of protecting genes against water deficit (WD), many of which are responsive to abscisic acid, the most important phytohormone to plants’ adaptation. This work aimed to recover abscisic acid (ABA)-responsive differentially expressed genes (DEG) from an RNA-Seq, carried out from leaves and roots of drought-sensitive (BR16) and tolerant (Embrapa 48) soybean cultivars under mild (MiWD), moderate (MoWD), and severe (SWD) water-deficit treatments. Enriched ABA-responsive pathways important to drought tolerance in soybean were also identified.ResultsIn drought-sensitive and tolerant soybean cultivars, approximately 75% of genes were identified as ABA-responsive by containing more than two ABRE (ABA-responsive elements) in the promoter region. Most of these genes were positively regulated. Roots were the tissue with more ABA-responsive genes and pathways triggered in response to WD in both cultivars, although, on the tolerant cultivar, these pathways were higher expressed. The most important enriched ABA pathways observed in the roots of both cultivars were involved in sugar and sulfur amino acid biosynthesis, osmoregulation, and crosstalk among ABA and ethylene, jasmonate, auxin, and cytokinin. Other pathways enriched were involved in phytoalexin production, ROS homeostasis, and membrane stability by glycerolipid and glycerophospholipid production. ABA-responsive genes were also ordered based on their expression profile in tissue and cultivar, and nine confidence groups could be observed. More than 80% of these clustered genes showed the same regulation profile under MiWd, MoWD, and SWD treatments. Activation of ABA biosynthesis under water deficit was validated by RT-qPCR by increasing the expression level of NCED3, an important enzyme in this pathway, and GOLS, a known ABA-responsive gene.ConclusionsA robust catalog of ABA-responsive genes was made available in this work. Considering ABA’s role in drought-response mechanisms, the genes in the groups pointed out in this study would be reliable candidates to be used in strategies to develop soybean lines more tolerant to drought. This paper, presented for the first time, ABA-responsive genes and ABA-enriched pathways in contrasting soybean cultivars for drought tolerance.

In soybean, studies on drought-responses are conducted during vegetative season. Information related to genes triggered in response to water-deficit (WD) in flower and pod is lacking. We performed an RNASeq and an agro-physiological characterization at stages R2 and R4 of soybean cultivar BR16, under WD. Physiological results showed a decrease in gas exchange parameters. Agronomical results showed WD impaired yield. Global Gene Ontology analyses indicated that most of the Differential Expressed Genes (DEGs) were down-regulated in flowers but up-regulated in pods. qRT-PCR revealed that WD triggered hormone biosynthesis changes. Mechanisms such as a decrease in glyceollin levels and cell wall instability were observed. This data showed tissue-specific mechanisms correlated with phenotypic responses such as drought escape, early flowering hormone-induced, and loss in grain weight. We presented here a comprehensive expression profile of flowers and pods soybean genes, which could guide researchers in the development of plants more tolerant to drought.