Background: The Hsp 20 genes are associated with stress caused by HS and other abiotic factors, but have recently been found to be associated with the response to biotic stresses. These genes represent the most abundant class among the HSPs in plants, but little is known about this gene family in soybean. Because of their apparent multifunctionality, these proteins are promising targets for developing crop varieties that are better adapted to biotic and abiotic stresses. Thus, in the present study an in silico identification of GmHsp 20 gene family members was performed, and the genes were characterized and subjected to in vivo expression analysis under biotic and abiotic stresses. Results: A search of the available soybean genome databases revealed 51 gene models as potential GmHsp 20 candidates. The 51 GmHsp 20 genes were distributed across a total of 15 subfamilies where a specific predicted secondary structure was identified. Based on in vivo analysis, only 47 soybean Hsp 20 genes were responsive to heat shock stress. Among the GmHsp 20 genes that were potentials HSR, five were also cold-induced, and another five, in addition to one GmAcd gene, were responsive to Meloidogyne javanica infection. Furthermore, one predicted GmHsp 20 was shown to be responsive only to nematode infection; no expression change was detected under other stress conditions. Some of the biotic stress-responsive GmHsp 20 genes exhibited a divergent expression pattern between resistant and susceptible soybean genotypes under M. javanica infection. The putative regulatory elements presenting some conservation level in the GmHsp 20 promoters included HSE, W-box, CAAT box, and TA-rich elements. Some of these putative elements showed a unique occurrence pattern among genes responsive to nematode infection. Conclusions: The evolution of Hsp 20 family in soybean genome has most likely involved a total of 23 gene duplications. The obtained expression profiles revealed that the majority of the 51 GmHsp 20 candidates are induced under HT, but other members of this family could also be involved in normal cellular functions, unrelated to HT. Some of the GmHsp 20 genes might be specialized to respond to nematode stress, and the predicted promoter structure of these genes seems to have a particular conserved pattern related to their biological function.

Soybean hosts a wide variety of pathogens that cause significant yield losses. The importance of soybean as a major oilseed crop has led to research focused on its interactions with pathogens, such as Soybean mosaic virus, Pseudomonas syringae, Phytophthora sojae, Phakopsora pachyrhizi, and Heterodera glycines. Pioneering work on soybean's interactions with these organisms, which represent the five major pathogen groups (viruses, bacteria, oomycetes, fungi, and nematodes), has contributed to our understanding of the molecular mechanisms underlying virulence and immunity. These mechanisms involve conserved and unique features that validate the need for research in both soybean and homologous model systems. In this review, we discuss identification of effectors and their functions as well as resistance gene–mediated recognition and signaling. We also point out areas in which model systems and recent advances in resources and tools have provided opportunities to gain deeper insights into soybean-pathogen interactions.

Strigolactones are a recently discovered class of carotenoid-derived plant hormones with a wide variety of functions, including acting as signaling molecules in the rhizosphere to promote arbuscular mycorrhizal fungi colonization and parasitic seed germination. To determine whether strigolactones influence the recruitment of microbes to the rhizosphere, we characterized both bacterial and fungal communities in response to the overexpression of genes involved in strigolactone biosynthesis (MAX1d) and signaling perception (D14 and MAX2a) in soybean (Glycine max). The amplicon sequencing-based results suggest that strigolactone overexpression lines had altered soybean rhizosphere bacteria composition at both the community level and individual taxa level with genera including Shinella and Bdellovibrio consistently more abundant across all three overexpression constructs. In addition, the responses of the soybean rhizosphere bacteria community differed significantly across the genes, with lines overexpressing genes involved in strigolactone biosynthesis (MAX1d) yielding a divergent bacterial community in comparison with those with altered expression of strigolactone perception genes (D14 and MAX2a). The overexpressed genes did not significantly impact the overall fungal community distribution; however, some individual taxa were altered in abundance. MAX1d and D14 overexpression lines had significantly enriched abundance of Fusarium solani. The mediating role of strigolactone biosynthesis and signaling genes on soybean rhizosphere bacterial and fungal communities confirmed strigolactone’s importance in the rhizosphere host–microbe communication and microbial community structure. [ ] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

With >7000 species the order of rust fungi has a disproportionately large impact on agriculture, horticulture, forestry and foreign ecosystems. The infectious spores are typically dikaryotic, a feature unique to fungi in which two haploid nuclei reside in the same cell. A key example is Phakopsora pachyrhizi, the causal agent of Asian soybean rust disease, one of the world’s most economically damaging agricultural diseases. Despite P. pachyrhizi’s impact, the exceptional size and complexity of its genome prevented generation of an accurate genome assembly. Here, we sequence three independent P. pachyrhizi genomes and uncover a genome up to 1.25 Gb comprising two haplotypes with a transposable element (TE) content of ~93%. We study the incursion and dominant impact of these TEs on the genome and show how they have a key impact on various processes such as host range adaptation, stress responses and genetic plasticity.

Soybean is the second largest source of oil worldwide. Developing soybean varieties with high levels of oleic acid is a primary goal of the soybean breeders and industry. Edible oils containing high level of oleic acid and low level of linoleic acid are considered with higher oxidative stability and can be used as a natural antioxidant in food stability. All developed high oleic acid soybeans carry two alleles; GmFAD2-1A and GmFAD2-1B. However, when planted in cold soil, a possible reduction in seed germination was reported when high seed oleic acid derived from GmFAD2-1 alleles were used. Besides the soybean fatty acid desaturase (GmFAD2-1) subfamily, the GmFAD2-2 subfamily is composed of five members, including GmFAD2-2A, GmFAD2-2B, GmFAD2-2C, GmFAD2-2D, and GmFAD2-2E. Segmental duplication of GmFAD2-1A/GmFAD2-1B, GmFAD2-2A/GmFAD2-2C, GmFAD2-2A/GmFAD2-2D, and GmFAD2-2D/GmFAD2-2C have occurred about 10.65, 27.04, 100.81, and 106.55 Mya, respectively. Using TILLING-by-Sequencing+ technology, we successfully identified 12, 8, 10, 9, and 19 EMS mutants at the GmFAD2-2A, GmFAD2-2B, GmFAD2-2C, GmFAD2-2D, and GmFAD2-2E genes, respectively. Functional analyses of newly identified mutants revealed unprecedented role of the five GmFAD2-2A, GmFAD2-2B, GmFAD2-2C, GmFAD2-2D, and GmFAD2-2E members in controlling the seed oleic acid content. Most importantly, unlike GmFAD2-1 members, subcellular localization revealed that members of the GmFAD2-2 subfamily showed a cytoplasmic localization, which may suggest the presence of an alternative fatty acid desaturase pathway in soybean for converting oleic acid content without substantially altering the traditional plastidial/ER fatty acid production.