Background: Drought is a major limiting factor seriously influencing worldwide soybean production and its impact on yield, morphological and physiological traits depend on the timing it occurs and the intensity of water shortage. Only limited research has however been conducted on identifying the drought-tolerant genotypes at different growth stages (vegetative growth phase, reproductive growth phase and the whole growth phase) as well as evaluate the effectiveness and reliability of multiple phenotypic and yield-related characteristics in soybean. Results: Two pot experiments and a 2-year field experiment were conducted to evaluate soybean drought tolerance at different growth stages. The membership function value of drought tolerance (MFVD) was used to identify drought-resistant cultivars during vegetative growth phase and reproductive growth stage; the relative drought index (RDI) of yield was used to assess drought-resistant cultivars during the whole growing period. In this study, regression models built based on MFVD indicated that the variation of drought tolerant coefficient (DC) of R/ S, TRL, LAI and RSR could explain 73.70% of the total variation at vegetative growth phase. However, higher heritability only found in LAI and RSR, indicating the two traits could serve as reliable criteria for drought evaluation. Similarly, the DC of SPP, YPP, PH, PB, MSNN and STB could explain 94.30% of the total variation in MFVD according to stepwise multiple linear regression analyses at reproductive growth phase. Thus, these six traits were identified as indicators for screening drought resistance genotypes in soybean. In addition, correlation analysis revealed that the MFVD was significantly positively correlated with the DC RB , DC R/S , DC RSA , DC RSR and DC RBR at vegetative growth phase and DC YPP , DC SPP , DC RB, and DC PB at reproductive growth phase. This indicated that these traits were closely related to the drought resistance of plants.

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Knowledge on the existing root diversity in germplasms has been emphasized for soybean breeding to improve drought resistance. Yet, evaluation of root diversity for vast genotypes still remains challenging. Here we investigated the contribution of different genotypic roots to drought resistance by a grafting experiment. A total of 22 cultivars were used as rootstocks to graft with scions of drought-sensitive cultivar L21. Water withholding was imposed during 15 days at podding stage in pot-culture experiments. The root-related traits were measured under wellwatered (WW) and water-stressed (WS) conditions. At maturity, the drought-resistance coefficient (DRC) was calculated as the yield under WS condition relative to WW yield. The DRC varied from 0.56 to 0.85 among grafts; thus, the rootstocks were categorized as drought-sensitive (DS), moderate (M) and drought-resistant (DR) types. The L21 scion grafted onto DR rootstocks resulted in higher DRC and greater drought resistance than those self-grafts. There were also significant interactions between water stress and genotype for root-related traits. With the increase of DRC, the plants showed linear increases in root length, root surface area, and root volume, but had linear decreases in root dry mass, root-shoot ratio and root tissue density under WS rather than WW conditions. We suggested that developed rooting with a low investment on dry matter identified by grafting experiments should be selected to improve drought resistance in soybean breeding.

Background Desmoplastic stroma, a feature of pancreatic ductal adenocarcinoma (PDAC), contains abundant activated pancreatic stellate cells (PSCs). How PSCs promote PDAC progression remains incompletely understood. Methods Effect of epithelium-specific E-twenty six factor 3 (ESE3)-positive PSCs on PDAC fibrosis and chemoresistance was examined by western blot, RT-PCR, immunofluorescence, flow cytometry assay, chromatin immunoprecipitation, luciferase assay, immunohistochemistry and subcutaneous pancreatic cancer mouse model. Results ESE3 expression increased in PSCs in PDAC tissues compared with those in normal PSCs. Clinical data showed that ESE3 upregulation in PSCs was positively correlated with tumour size, pTNM stage, CA19-9, carcinoembryonic antigen and serum CA242 level. ESE3 overexpression in PSCs was an independent negative prognostic factor for disease-free survival and overall survival amongst patients with PDAC. Mechanistically, the conditional medium from the loss and gain of ESE3-expressing PSCs influenced PDAC chemoresistance and tumour growth. ESE3 directly induced the transcription of α-SMA, collagen-I and IL-1β by binding to ESE3-binding sites on their promoters to activate PSCs. IL-1β upregulated ESE3 in PSCs through NF-κB activation, and ESE3 was required for PSC activation by tumour cell-derived IL-1β. Conclusion Inhibiting the IL-1β/ESE3 (PSCs)/IL-1β-positive feedback loop is a promising therapeutic strategy to reduce tumour fibrosis and increase chemotherapeutic efficacy in PDAC.