Biology subjects

Kovinich, N.

Publications and source records attributed to Kovinich, N..

3 recordsLinked to original sources

bioRxiv2025

Soybean aphids exploit abscisic acid signaling to suppress jasmonate defense responses

SummaryO_LISoybean aphids (Aphis glycines) can induce susceptibility on soybean (Glycine max) during colonization. However, the mechanism for this process is not known. Based on previous transcriptome analyses, we hypothesized that aphids block effective jasmonate (JA) defenses by inducing an antagonistic abscisic acid (ABA) signal. C_LIO_LITo test this hypothesis, we used a combination of gene expression analyses, measurements of hormone levels, and aphid bioassays on plants with reduced expression of ABA-related genes. C_LIO_LIAphid feeding attenuated JA responses in soybean plants and facilitated the growth of a chewing herbivore. Aphid-treated plants had increased levels of cis-JA but not biologically active JA-isoleucine, and aphid feeding induced expression of genes associated with JA-Ile catabolism. In parallel, aphid-feeding induced higher levels of ABA. ABA treatment and knockdown lines impaired in ABA biosynthesis (aba2-RNAi) or signaling (scof-1-RNAi), showed that ABA suppressed wound-induced JA responses. Aphid populations were significantly reduced on ABA-deficient plants and aphid-regulated attenuation of JA signaling was abolished in these lines. Remarkably, plants defective in ABA signaling had increased JA signaling in the absence of stressors. C_LIO_LIOur results indicate that, in soybean, the ABA pathway is necessary to control basal levels of JA and soybean aphids exploit this ABA-JA antagonism to suppress plant defenses. C_LI

plant biology↗

bioRxiv2024

ABA-regulated JAZ1 Proteins Bind NAC42 Transcription Factors to Suppress the Activation of Phytoalexin Biosynthesis in Plants

Phytoalexins are plant defense metabolites whose biosynthesis remains suppressed until elicited by a pathogen or stress, yet the mechanism of their suppression has remained elusive. The transcription factor GmNAC42-1 is an important and direct activator of the biosynthesis of glyceollin phytoalexins in soybean. Yet, without elicitation, overexpressing GmNAC42-1 is insufficient to activate the expression of glyceollin biosynthetic genes, suggesting that the activity of GmNAC42-1 may be suppressed by a negative regulator. JAZ1 proteins are negative regulators of the canonical jasmonic acid (JA) signaling pathway. JAZ protein degradation and JAZ gene transcription comprise antagonistic mechanisms that activate and suppress JA signaling, respectively. In search for negative regulators of glyceollin biosynthesis, we identified by RNA-seq analysis abscisic acid (ABA) signaling and GmJAZ1 genes that are oppositely regulated compared to glyceollin biosynthesis. Long-term ABA treatment upregulated GmJAZ1 transcripts, whereas its biosynthesis inhibitor fully suppressed their upregulation by dehydration stress. Opposite patterns were observed for glyceollin biosynthesis. RNAi silencing of GmJAZ1s prevented the suppression of glyceollin biosynthesis by dehydration and derepressed glyceollin synthesis in non-elicited tissues. Overexpressing GmJAZ1-9 in hairy roots elicited with Phytophthora sojae wall glucan elicitor partially suppressed glyceollin biosynthesis. The GmJAZ1-9 protein physically interacted with GmNAC42-1 and inhibited its transactivation and DNA binding activities in promoter-luciferase and yeast-three hybrid systems. Silencing JAZ1s in Arabidopsis and grapevine has been reported to derepress camalexin and stilbene phytoalexin biosynthesis. Here, we found that JAZ1 and NAC42 proteins from all three plant species physically interact, suggesting a conserved mechanism negatively regulates phytoalexin biosynthesis in plants. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC="FIGDIR/small/615281v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@127cf6borg.highwire.dtl.DTLVardef@a2aa9borg.highwire.dtl.DTLVardef@16ebe08org.highwire.dtl.DTLVardef@17e1cad_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2024

Discovery of the missing cytochrome P450 monooxygenase cyclases that conclude glyceollin biosynthesis in soybean

Glyceollins are isoflavonoid-derived metabolites produced by soybean that hold great promise in improving human and animal health due to their antimicrobial, and other medicinal properties. They play important roles in agriculture by defending soybean against one of its most destructive pathogens, Phytophthora sojae. Longstanding research efforts have focused on improving accessibility to glyceollins, yet chemical synthesis remains uneconomical. The fact that some of the key genes involved in the final step of glyceollin biosynthesis have not been identified, engineering the accumulation of these important compounds in microbes is not yet possible. Although the activity of a P450 cyclase was inferred to catalyze the final committed step in glyceollin biosynthesis forty years ago, the enzyme in question has never been conclusively identified. This study reports, for the first time, the identification of three cytochrome P450 monooxygenase cyclases that catalyze the final steps of glyceollin biosynthesis. Utilizing P. sojae-soybean transcriptome data, along with genome mining tools and co-expression network analysis, we have identified 16 candidate glyceollin synthases (GmGS). Heterologous expression of these candidate genes in yeast, coupled with in vitro enzyme assays, enabled us to discover three enzymes capable of producing two glyceollin isomers. GmGS11A and GmGS11B catalyzed the conversion of glyceollidin to glyceollin I, whereas GmGS13A converted glyceocarpin to glyceollin III. The functionality of these candidates was further confirmed in planta through gene silencing and overexpression in soybean hairy roots. This groundbreaking study not only contributes to the understanding of glyceollin biosynthesis, but also demonstrates a new synthetic biology strategy that could potentially be scaled up to produce valuable molecules for crop and disease management.

biochemistry↗