Soybean cyst nematode (SCN;
- Award ID(s):
- 1556370
- NSF-PAR ID:
- 10220133
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary Heterodera glycines ) is the largest pathogenic cause of soybean yield loss. TheRhg1 locus is the most used and best characterized SCN resistance locus, and contains three genes including one encoding an α‐SNAP protein. Although theRhg1 α‐SNAP is known to play an important role in vesicle trafficking and SCN resistance, the protein’s binding partners and the molecular mechanisms underpinning SCN resistance remain unclear. In this report, we show that theRhg1 α‐SNAP strongly interacts with two syntaxins of the t‐SNARE family (Glyma.12G194800 and Glyma.16G154200) in yeast and plants; importantly, the genes encoding these syntaxins co‐localize with SCN resistance quantitative trait loci. Fluorescent visualization revealed that the α‐SNAP and the two interacting syntaxins localize to the plasma membrane and perinuclear space in both tobacco epidermal and soybean root cells. The two syntaxins and their two homeologs were mutated, individually and in combination, using the CRISPR‐Cas9 system in the SCN‐resistant Peking and SCN‐susceptible Essex soybean lines. Peking roots with deletions introduced into syntaxin genes exhibited significantly reduced resistance to SCN, confirming that t‐SNAREs are critical to resisting SCN infection. The results presented here uncover a key step in the molecular mechanism of SCN resistance, and will be invaluable to soybean breeders aiming to develop highly SCN‐resistant soybean varieties. -
Abstract Soybean growers widely use the
R esistance to 1 (H eteroderag lycinesRhg1 ) locus to reduce yield losses caused by soybean cyst nematode (SCN).Rhg1 is a tandemly repeated four gene block. Two classes of SCN resistance‐conferringRhg1 haplotypes are recognized:rhg1‐a (“Peking‐type,” low‐copy number, three or fewerRhg1 repeats) andrhg1‐b (“PI 88788‐type,” high‐copy number, four or moreRhg1 repeats). Therhg1‐a andrhg1‐b haplotypes encode α‐SNAP (alpha‐S olubleN SFA ttachmentP rotein) variants α‐SNAPRhg1 LC and α‐SNAPRhg1 HC, respectively, with differing atypical C‐terminal domains, that contribute to SCN resistance. Here we report thatrhg1‐a soybean accessions harbor a copia retrotransposon within theirRhg1 Glyma.18G022500 (α‐SNAP‐encoding) gene. We termed this retrotransposon “RAC, ” forR hg1a lpha‐SNAPc opia. Soybean carries multipleRAC ‐like retrotransposon sequences. TheRhg1 RAC insertion is in theGlyma.18G022500 genes of all truerhg1‐a haplotypes we tested and was not detected in any examinedrhg1‐b orRhg1WT (single‐copy) soybeans.RAC is an intact element residing within intron 1, anti‐sense to therhg1‐a α‐SNAP open reading frame.RAC has intrinsic promoter activities, but overt impacts ofRAC on transgenic α‐SNAPRhg1 LC mRNA and protein abundance were not detected. From the nativerhg1‐a RAC+ genomic context, elevated α‐SNAPRhg1 LC protein abundance was observed in syncytium cells, as was previously observed for α‐SNAPRhg1 HC (whoserhg1‐b does not carryRAC ). Using a SoySNP50K SNP corresponding withRAC presence, just ~42% of USDA accessions bearing previously identifiedrhg1‐a SoySNP50K SNP signatures harbor theRAC insertion. Subsequent analysis of several of these putativerhg1‐a accessions lackingRAC revealed that none encodedα‐SNAPRhg1LC , and thus, they are notrhg1‐a .rhg1‐a haplotypes are of rising interest, withRhg4 , for combating SCN populations that exhibit increased virulence against the widely usedrhg1‐b resistance. The present study reveals another unexpected structural feature of manyRhg1 loci, and a selectable feature that is predictive ofrhg1‐a haplotypes. -
Two amino acid variants in soybean serine hydroxymethyltransferase 8 (SHMT8) are associated with resistance to the soybean cyst nematode (SCN), a devastating agricultural pathogen with worldwide economic impacts on soybean production. SHMT8 is a cytoplasmic enzyme that catalyzes the pyridoxal 5‐phosphate‐dependent conversion of serine and tetrahydrofolate (THF) to glycine and 5,10‐methylenetetrahydrofolate. A previous study of the P130R/N358Y double variant of SHMT8, identified in the SCN‐resistant soybean cultivar (cv.) Forrest, showed profound impairment of folate binding affinity and reduced THF‐dependent enzyme activity, relative to the highly active SHMT8 in cv. Essex, which is susceptible to SCN. Given the importance of SCN‐resistance in soybean agriculture, we report here the biochemical and structural characterization of the P130R and N358Y single variants to elucidate their individual effects on soybean SHMT8. We find that both single variants have reduced THF‐dependent catalytic activity relative to Essex SHMT8 (10‐ to 50‐fold decrease in
k cat/K m) but are significantly more active than the P130R/N368Y double variant. The kinetic data also show that the single variants lack THF‐substrate inhibition as found in Essex SHMT8, an observation with implications for regulation of the folate cycle. Five crystal structures of the P130R and N358Y variants in complex with various ligands (resolutions from 1.49 to 2.30 Å) reveal distinct structural impacts of the mutations and provide new insights into allosterism. Our results support the notion that the P130R/N358Y double variant in Forrest SHMT8 produces unique and unexpected effects on the enzyme, which cannot be easily predicted from the behavior of the individual variants. -
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