Biology subjects

Bent, A. F.

Publications and source records attributed to Bent, A. F..

6 recordsLinked to original sources

bioRxiv2026

AATRhg1 is a tonoplast protein that alters amino acid, metabolic and defense responses and nematode resistance

Soybean cyst nematode (SCN, Heterodera glycines) causes significant soybean yield losses. The Rhg1 locus is a major contributor to SCN resistance and contains three genes that mediate this trait including Rhg1-GmAAT (Glyma.18G022400), which encodes putative amino acid transporter AATRhg1. The molecular function of AATRhg1 in SCN resistance is not understood. In this study, rhg1-b soybean lines with Rhg1-GmAAT silencing demonstrated that Rhg1-GmAAT can contribute resistance against HG 0 SCN and also against problematic HG 2.5.7 populations that partially overcome rhg1-b-mediated resistance. An AATRhg1 Y268L mutant complemented SCN resistance in Rhg1-GmAAT-silenced plants while an AATRhg1 D122A mutant did not. Overexpression of Rhg1-GmAAT was not sufficient to enhance SCN resistance, suggesting that AATRhg1 requires coordinated activity with other proteins or pathways. Confocal microscopy demonstrated that AATRhg1 localizes to the tonoplast in soybean root cells. Amino acid, transcriptomic and metabolomic profiles were determined for SCN-infected root segments 3 days after SCN inoculation. In Rhg1-GmAAT-silenced plants relative to fully resistant (non-silenced) rhg1-b plants, levels of leucine, isoleucine, and tyrosine were significantly elevated. Rhg1-GmAAT silencing reduced SCN-responsive transcript abundances for multiple processes, significantly including genes for MAPK signaling, ethylene responses and starch and sucrose metabolism. The most common identified metabolomic changes were in amino acid derivatives, shikimate/phenylpropanoid/isoflavonoid compounds, terpenoids, and especially fatty acids. These findings can guide further investigation into the mechanisms by which AATRhg1 contributes to SCN resistance.

plant biology↗

bioRxiv2025

Soybean Rhg1 resistance to Heterodera glycines impedes theparasitism of Pratylenchus penetrans

Rhg1 has been the most effective QTL deployed in soybeans (Glycine max) to control soybean cyst nematode (Heterodera glycines; SCN). However, the resistance mechanisms and specificity of Rhg1 towards SCN as opposed to other plant parasitic nematodes are not well known. In this study we report that Rhg1 can hinder the parasitism of the root lesion nematode Pratylenchus penetrans (Pp), which is commonly found along with SCN in northern U.S. soybean fields. Two elite public soybean varieties, carrying either rhg1-a + Rhg4 or rhg1-b, negatively impacted Pp populations measured at 30 dpi. This contribution of Rhg1 was more rigorously demonstrated using near isogenic lines for rhg1-b. Additionally, in three of the four soybean genetic backgrounds tested we observed significantly more Pp at 30 dpi when Pp were co-inoculated with SCN, consistent with a previous study. No significant changes in SCN cyst numbers upon co-inoculation with Pp were observed for any of the SCN-resistant rhg1 lines. No nematode-induced changes in Rhg1 transcript abundances were observed when sampling infected root sections in any of the plant genotypes, and no changes in a jasmonate response indicator were observed. However, the 3 dpi salicylate-mediated response to SCN or Pp became more robust during SCN + Pp co-infection. Multiple hypotheses for further dissection and manipulation of soybean resistance to Pratylenchus root lesion nematodes are suggested based on the present findings.

plant biology↗

bioRxiv2024

Soybean Cyst Nematode-Resistant Protein AATRhg1 Affects Amino Acid Homeostasis and Betalain Accumulation

Amino acid transporters play crucial roles in plant nitrogen metabolism but also defense responses. AATRhg1, an apparent amino acid transporter encoded by Glyma.18g022400 (Rhg1-GmAAT) at the soybean Rhg1 locus, contributes to resistance to soybean cyst nematode (SCN), although the in planta function of AATRhg1 remains elusive. In this study we discovered that overexpression of Rhg1-GmAAT in soybean roots enhances the betalain pigment synthesis driven by a RUBY transgene cassette, potentially through its transporter activity affecting tyrosine level and amino acid homeostasis. Silencing Rhg1-GmAAT also moderately increased betalain accumulation while co-overexpression of Rhg1-GmAAT and GmRBOHG (encoding an AATRhg1-interacting NADPH oxidase) blocked the betalain phenotype, indicating a complex role of AATRhg1 in regulating cellular metabolism. Soybean AATRhg1 did not show a betalain accumulation phenotype when co-overexpressed with RUBY in Nicotiana benthamiana leaves, suggesting that soybean AATRhg1 functions differently in N. benthamiana. In soybean, the expression of AATRhg1 proteins mutated at conserved residues D122A or Y268L mitigated or enhanced the betalain phenotypes, respectively, suggesting that these residues are important for AATRhg1 function. This study advances our understanding of AATRhg1 while presenting a novel strategy for enhancing betalain biosynthesis by modulating transport and homeostasis of amino acids.

plant biology↗

bioRxiv2024

Overexpression of α-SNAPRhg1 can improve rhg1-a mediated soybean resistance to soybean cyst nematode

(i)The rhg1-a and rhg1-b haplotypes of the soybean Rhg1 locus are economically effective tools for the control of soybean cyst nematode (SCN; Heterodera glycines), but ongoing SCN evolution requires improved sources of resistance. Both Rhg1 haplotypes carry multiple tandem repeat copies of a four-gene block encoding four disparate proteins; resistance efficacy scales with copy number. The haplotypes encode different variants of an unusual -SNAP protein whose abundance increases in the nematode-reprogrammed plant cells that form the syncytium (nematode feeding site), which subsequently collapses. Simultaneous presence of the two -SNAPRhg1 protein types, or substantially elevated expression of either type, was hypothesized to improve SCN resistance but has not been achievable by conventional plant breeding methods. We accomplished both, by transgenic additions to an rhg1-a Rhg4 soybean line. Existing resistance to HG type 0 and HG type 2.5.7 SCN was strengthened, but resistance was not improved against an HG type 1.3.6.7 SCN population that was already highly virulent on the parent line. No significant yield penalties from constitutive overexpression of transgenic -SNAP genes were observed in greenhouse or initial field studies. Cisgenic combination or elevated expression of the different -SNAP genes may extend the efficacy and/or durability of Rhg1-mediated resistance. We also observed differential protein abundances for some -SNAPRhg1 isoforms after inoculation with different HG type populations of SCN. These approaches provide opportunities to understand the different mechanisms of the two Rhg1 haplotypes and to possibly fine-tune them for better management of SCN.

plant biology↗

bioRxiv2020

The soybean Rhg1 amino acid transporter protein becomes abundant along the SCN penetration path and impacts ROS generation

Rhg1 mediates soybean resistance to soybean cyst nematode. Glyma.18G022400, one of three resistance-conferring genes at the complex Rhg1 locus, encodes the putative amino acid transporter AATRhg1 whose mode of action is largely unknown. We discovered that AATRhg1 protein abundance increases 7- to 15-fold throughout root cells penetrated by SCN. These root cells develop increased abundance of vesicles and larger vesicle-like bodies. AATRhg1 was often associated with these vesicles. AATRhg1 abundance remained low in syncytia (plant reprogrammed feeding cells), unlike the Rhg1 -SNAP protein whose abundance was previously shown to increase in syncytia. In N. benthamiana, if soybean AATRhg1 was present, oxidative stress promoted formation of larger macrovesicles and they contained AATRhg1. AATRhg1 was found to interact with GmRBOHC2, a soybean ortholog of Arabidopsis RBOHD previously found to exhibit upregulated expression upon SCN infection. Reactive oxygen species (ROS) generation was more elevated when AATRhg1 and GmRBOHC2 abundance were co-expressed. These findings suggest that AATRhg1 contributes to SCN resistance along the penetration path as SCN invades the plant, and does so at least in part by interactions with GmRBOHC2 that increase ROS production. The study also shows that Rhg1 resistance functions via at least two spatially and temporally separate modes of action.

plant biology↗

bioRxiv2019

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

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.

plant biology↗