Down-regulation of Fra a 1.02 in strawberry fruits causes transcriptomic and metabolic changes compatible with an altered defense response

Abstract

The strawberry Fra a 1 proteins belong to the class 10 Pathogenesis-Related (PR-10) superfamily. In strawberry, a large number of members have been identified, but only a limited number is expressed in the fruits. In this organ, Fra a 1.01 and Fra a 1.02 are the most abundant Fra proteins in the green and red fruits, respectively, however, their function remains unknown. To know the function of Fra a 1.02 we have generated transgenic lines that silence this gene, and performed metabolomics, RNA-Seq, and hormonal assays. Previous studies associated Fra a 1.02 to strawberry fruit color, but the analysis of anthocyanins in the ripe fruits showed no diminution in their content in the silenced lines. Gene ontology (GO) analysis of the genes differentially expressed indicated that oxidation/reduction was the most represented biological process. Redox state was not apparently altered since no changes were found in ascorbic acid and glutathione (GSH) reduced/oxidized ratio, but GSH content was reduced in the silenced fruits. In addition, a number of glutathione-S-transferases (GST) were down-regulated as result of Fra a 1.02-silencing. Another highly represented GO category was transport which included a number of ABC and MATE transporters. Among the regulatory genes differentially expressed WRKY33.1 and WRKY33.2 were down-regulated, which had previously been assigned a role in strawberry plant defense. A reduced expression of the VQ23 gene and a diminished content of the hormones JA, SA, and IAA were also found. These data might indicate that Fra a 1.02 participates in the defense against pathogens in the ripe strawberry fruits.

Microscale Thermophoresis Reveals Oxidized Glutathione as High-Affinity Ligand of Mal d 1

“…Similarly, previous studies have further proposed that the loss of GST function can cause a reduction in anthocyanidin accumulation in concert with the loss of color development in other plants, such as MdGST in apple, VviGST4 in grape, LcGST4 in litchi, and RAP in strawberry [60][61][62][63]. More recently it was shown that the stable downregulation of the PR-10 protein Fra a 1 triggered decreased GSH concentration and lower GST expression levels in the transgenic fruits (Figure 4) [64]. As additional endorsement, our results demonstrate the binding of GSH and GSSG to the PR-10 protein Mal d 1, which may be of significance for the regulation of the anthocyanin/flavonoid accumulation in apples.…”

Possible mechanism of contribution of a secreted aspartic proteinase FpOPSB to the virulence of Fusarium proliferatum causing banana crown rot

“…Most of them have been reported to positively regulate plant defense responses against pathogens. For instance, PR‐10 superfamily participates in the defense against pathogens in the ripe strawberry fruits (Orozco‐Navarrete et al., 2021). In addition, previous research hypothesized that overexpression of the gene encoding nonsymbiotic hemoglobin can interfere in the dynamics of ROS production and NO scavenging, and then reduce plant susceptibility to Meloidogyne incognita (Basso et al., 2022).…”

Elusive partners: a review of the auxiliary proteins guiding metabolic flux in flavonoid biosynthesis

“…A recent report found that priming strawberry leaves with the phytohormone salicylic acid (SA) leads to upregulation of PR genes, including PR10 genes, and concomitant increases in PA levels (Feng et al., 2020). In another study, silencing Fra a 1.02 led to downregulation of WRKY‐type transcription factors and ABC and MATE transporters and to a diminished content of the hormones jasmonic acid, SA, and indole acetic acid, suggesting a role in stress responses (Orozco‐Navarrete et al., 2021). This report and others indicate that stress‐induced expression of PR10s, including Fra a proteins, can potentially orchestrate a metabolic shift via undiscovered roles as auxiliary proteins, chemical chaperones, or regulatory elements.…”