Gene Expression in Cucurbita spp. Root and Crown during Phytophthora capsici Infection

Abstract

Phytophtora capsici causes major diseases in cucurbit crops worldwide. In this study, we inoculated this pathogen into Cucurbita pepo subsp. pepo susceptible MUCU-16 and C. moschata tolerant M63. The gene expression of plant pathogenesis-related proteins chitinase (CpChiIV), lignin-forming peroxidase (CpLPOX), and defensin (CpDEF) and hormone-related enzymes salicylic acid (CpPAL) and ethylene (CpACO) was analyzed for two weeks post-inoculation in root and crown tissues. Differentially expressed genes were found between genotypes, tissues, days post-inoculation, and inoculated/non-inoculated samples. After inoculation, CpPAL and CpChiIV (crown) were downregulated in MUCU-16, while CpLPOX and CpDEF were upregulated in M63. In inoculated samples, higher expression changes were presented on days 10–14 than on day 3 for CpACO, CpLPOX, and CpDEF genes. Overexpression was higher for CpDEF compared to the other tested genes, indicating good suitability as a marker of biotic stress. The overexpression of CpDEF was higher in crown than in roots for both inoculated genotypes. The basal expression of CpPAL and CpDEF was higher in MUCU-16, but after inoculation, CpPAL and CpDEF gene expression were higher in M63. These changes suggest an association between CpDEF upregulation and tolerance, and between CpPAL downregulation and susceptibility.

Tolerance Screening for Phytophthora capsici and Fusarium solani f. sp. cucurbitae in Cucurbita spp. and Gene Expression Responses in Mutant Families

“…The CpDEF gene was highly overexpressed in the inoculated plants, and CpPAL downregulation occurred only in the susceptible genotypes, which is in agreement with previous studies [34]. Moreover, The mutants Cp107 and Cp116 expressed more CpChiIV than MUCU-16 after inoculation.…”

“…Gene expression changes in CpChiIV (EP3 endochitinase) [29], CpLPOX (ligninforming peroxidase) [30,31], CpDEF (J1-2-like defensin) [31,32], CpPAL (phenylalanine ammonia-lyase) [31,33], and CpACO (1-aminocyclopropane-1-carboxylate oxidase) [31] were previously tested in the Cucurbita spp. and P. capsici pathosystem [34]. Differential responses in CpDEF (higher upregulation with tolerance) and CpPAL (down-regulation with susceptibility) were found between tolerant and susceptible Cucurbita phenotypes inoculated with P. capsici [34].…”

“…and P. capsici pathosystem [34]. Differential responses in CpDEF (higher upregulation with tolerance) and CpPAL (down-regulation with susceptibility) were found between tolerant and susceptible Cucurbita phenotypes inoculated with P. capsici [34].…”

“…Each sample was extracted from eight different plants, which decreased the number of plants in the test by eight after each sample collection day. Sample collection, RNA extraction, and cDNA obtention were performed as described in previous work [34]. The primers (Sigma-Aldrich, St. Louis, MO, USA), except for the UFP and EFP-1α reference genes [37], were obtained from previous work [34].…”

“…Sample collection, RNA extraction, and cDNA obtention were performed as described in previous work [34]. The primers (Sigma-Aldrich, St. Louis, MO, USA), except for the UFP and EFP-1α reference genes [37], were obtained from previous work [34]. The qPCR cycling conditions were: 50 • C 2 ; 95 • C 10 ; 40× (95 • C 15", 55 • C 15 , and 60 • C 1"); and melting (95 • C 15", 5 of 14 60 • C 1 , and 95 • C 1").…”