bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/653568

The rhg1-a (Rhg1 low-copy) nematode resistance source harbors a copia-family retrotransposon within the Rhg1-encoded α-SNAP gene

Bayless, A. M.·Zapotocny, R. W.·Han, S.·Grunwald, D. J.·Amundson, K. K.·Bent, A. F.
View original source ↗Export metadata ↓

Abstract

Soybean growers widely use the Resistance to Heterodera glycines 1 (Rhg1) locus to reduce yield losses caused by soybean cyst nematode (SCN). Rhg1 is a tandemly repeated four gene block. Two classes of SCN resistance-conferring Rhg1 haplotypes are recognized: rhg1-a (\"Peking-type\", low copy number, 3 or fewer Rhg1 repeats) and rhg1-b (\"PI 88788-type\", high copy number, 4 or more Rhg1 repeats). The rhg1-a and rhg1-b haplotypes encode -SNAP (alpha-Soluble NSF Attachment Protein) variants -SNAPRhg1LC and -SNAPRhg1HC respectively, with differing atypical C-terminal domains, that contribute to SCN-resistance. Here we report that rhg1-a soybean accessions harbor a copia retrotransposon within their Rhg1 Glyma.18G022500 (-SNAP-encoding) gene. We termed this retrotransposon \"RAC\", for Rhg1 alpha-SNAP copia. Soybean carries multiple RAC-like retrotransposon sequences. The Rhg1 RAC insertion is in the Glyma.18G022500 genes of all true rhg1-a haplotypes we tested and was not detected in any examined rhg1-b or Rhg1WT (single-copy) soybeans. RAC is an intact element residing within intron 1, anti-sense to the rhg1-a -SNAP open reading frame. RAC has intrinsic promoter activities, but overt impacts of RAC on transgenic -SNAPRhg1LC mRNA and protein abundance were not detected. From the native rhg1-a RAC+ genomic context, elevated -SNAPRhg1LC protein abundance was observed in syncytium cells, as was previously observed for -SNAPRhg1HC (whose rhg1-b does not carry RAC). Using a SoySNP50K SNP corresponding with RAC presence, just [~]42% of USDA accessions bearing previously identified rhg1-a SoySNP50K SNP signatures harbor the RAC insertion. Subsequent analysis of several of these putative rhg1-a accessions lacking RAC revealed that none encoded -SNAPRhg1LC, and thus they are not rhg1-a. rhg1-a haplotypes are of rising interest, with Rhg4, for combating SCN populations that exhibit increased virulence against the widely used rhg1-b resistance. The present study reveals another unexpected structural feature of many Rhg1 loci, and a selectable feature that is predictive of rhg1-a haplotypes.

Source connections

Explore related subjects

plant biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Bayless, A. M., Zapotocny, R. W., Han, S., Grunwald, D. J., Amundson, K. K., Bent, A. F.. 2019-05-30. The rhg1-a (Rhg1 low-copy) nematode resistance source harbors a copia-family retrotransposon within the Rhg1-encoded α-SNAP gene. https://doi.org/10.1101/653568

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Secondary growth in the tomato stem is suppressed by the flowering regulators FUL2 and STM3

Herbaceous eudicot crops such as tomato accumulate substantial amounts of secondary xylem in their stems, particularly in the basal part. As plants progress from the vegetative phase to flowering and fruit development, secondary growth continues to provide mechanical support and facilitate transport. To uncover how secondary growth is regulated in the tomato stem, we used laser capture microdissection RNA-seq to establish tissue-specific transcriptomic profiles. This revealed that key regulators associated with wood formation in poplar are also acting in tomato. Furthermore, we found that the flowering regulators FUL2 and STM3 are substantially expressed in xylem tissue. Subsequent functional analysis identified FUL2 and STM3 as key repressors of secondary growth, with ful2 or stm3 knock-out mutants exhibiting strongly increased secondary growth in older tomato stems. Notably, a higher order mutant in which both ful2 and stm3 were knocked out displays a similar non-additive phenotype, indicating, together with yeast two-hybrid data showing physical interaction, that FUL2 and STM3 act together in a complex. The expression levels of both genes remain low until after the floral transition but strongly rise during subsequent stem development. Transcriptomic analyses in ful2, stm3, and wild-type stems at stages before and after detectable anatomical differences, showed that the FUL2-STM3 complex represses distinct sets of NAC and MYB candidate regulators associated with xylem development. Interestingly, FUL2 and STM3 control these regulators in a stage- and position-dependent way, with candidates showing upregulation only at later stages in mid-height stems being already upregulated at earlier stages in basal stem regions. Our findings provide a tissue-resolved transcriptomic resource for tomato stems and reveal a role for FUL2 and STM3 in limiting secondary xylem accumulation as stem development progresses.

plant biology↗
bioRxiv2026

Geometric Morphometrics of Pistillate Flowers in Astrocaryum sect. Huicungo (Arecaceae): Taxonomic Implications for the Peruvian Species

The taxonomy of the Amazonian palm clade Astrocaryum sect. Huicungo remains controversial due to deep discordances between traditional classifications based on qualitative floral traits and recent phylogenomic evidence. To address this, landmark-based two-dimensional geometric morphometrics (4 landmarks, 16 semilandmarks) was applied to evaluate the symmetric component of shape variation in calyx and corolla structures across 549 pistillate flowers from the 11 Peruvian species. Although multivariate analyses (PCA, CVA) revealed continuous morphological variation and extensive phenotypic overlap, perianth geometry retained a significant diagnostic signal. Cross-validated classification rates demonstrated that the corolla exhibited higher discriminatory power than the calyx, while the combined perianth analysis (calyx + corolla) maximized taxonomic assignment accuracy. Furthermore, Mahalanobis distance-based clustering did not replicate traditional subsections: A. chonta and A. ulei exhibited divergent architectures, whereas A. carnosum, A. faranae, and A. huicungo shared profound geometric similarity. This study demonstrates that quantitative perianth morphometrics is a valuable tool for species delimitation in Astrocaryum, supporting the re-evaluation of traditional taxonomic boundaries through an integrative approach.

plant biology↗
bioRxiv2026

Multi-Criteria Evaluation of Hibiscus mutabilis Cultivars for Food Development Using Delphi and Analytic Hierarchy Process

This study evaluated 11 Hibiscus mutabilis cultivars from Chengdu Botanical Garden to assess their quality for food use and identify promising cultivars. An evaluation framework was developed using the Delphi method to select indicators and the analytic hierarchy process (AHP) to determine their weights. Overall scores ranged from 2.5785 to 3.6043, and the cultivars were classified into three grades. Grade I included Hibiscus mutabilis 'Bairi Huacai', Hibiscus mutabilis 'Chongbanbai' and Hibiscus mutabilis 'Jinqiusong'; Grade II included Hibiscus mutabilis 'Jinqiuhong', Hibiscus mutabilis 'Zuifurong', Hibiscus mutabilis 'Danbanhong', Hibiscus mutabilis 'Jinxiuzi', Hibiscus mutabilis 'Jinbiyu' and Hibiscus mutabilis 'Caixia'; whereas Grade III included Hibiscus mutabilis 'Mudanfen' and Hibiscus mutabilis 'Jinrui'. In summary, Hibiscus mutabilis 'Bairi Huacai', Hibiscus mutabilis 'Chongbanbai' and Hibiscus mutabilis 'Jinqiusong' are the preferred cultivars for food processing and development. The framework provides a basis for cultivar screening and further evaluation of H. mutabilis flowers for food use.

plant biology↗