The CaChiVI2 Gene of Capsicum annuum L. Confers Resistance Against Heat Stress and Infection of Phytophthora capsici

Abstract

Extreme environmental conditions seriously affect crop growth and development, resulting in substantial reduction in yield and quality. However, chitin-binding proteins (CBP) family member CaChiVI2 plays a crucial role in eliminating the impact of adverse environmental conditions, such as cold and salt stress. Here, for the first time it was discovered that CaChiVI2 (Capana08g001237) gene of pepper (Capsicum annuum L.) had a role in resistance to heat stress and physiological processes. The full-length open-reading frame (ORF) of CaChiVI2 (606-bp, encoding 201-amino acids), was cloned into TRV2:CaChiVI2 vector for silencing. The CaChiVI2 gene carries heat shock elements (HSE, AAAAAATTTC) in the upstream region, and thereby shows sensitivity to heat stress at the transcriptional level. The silencing effect of CaChiVI2 in pepper resulted in increased susceptibility to heat and Phytophthora capsici infection. This was evident from the severe symptoms on leaves, the increase in superoxide (O 2 −) and hydrogen peroxide (H 2 O 2) accumulation, higher malondialdehyde (MDA), relative electrolyte leakage (REL) and lower proline contents compared with control plants. Furthermore, the transcript level of other resistance responsive genes was also altered. In addition, the CaChiIV2-overexpression in Arabidopsis thaliana showed mild heat and drought stress symptoms and increased transcript level of a defense-related gene (AtHSA32), indicating its role in the co-regulation network of the plant. The CaChiVI2overexpressed plants also showed a decrease in MDA contents and an increase in antioxidant enzyme activity and proline accumulation. In conclusion, the results suggest that CaChiVI2 gene plays a decisive role in heat and drought stress tolerance, as well as, provides resistance against P. capsici by reducing the accumulation of reactive oxygen species (ROS) and modulating the expression of defense-related genes. The outcomes obtained here suggest that further studies should be conducted on plants adaptation mechanisms in variable environments.

Chitinase Gene Positively Regulates Hypersensitive and Defense Responses of Pepper to Colletotrichum acutatum Infection

“…This resulted in the observation of 34% more lesions (infection) in the pTRV2:CaChiIII7 plants compared with pTRV2:00 (control), demonstrating that the silencing of chitinase gene CaChiIII7 greatly increased the sensitivity to C. acutatum infection ( Figure 4C and D). Parallel results in the same crop have been observed in which the silencing of CaChiIV1 and CaChiVI2 decreased resistance against Phytophthora blight [27,28]. The knockdown of CaChiIII7 also substantially affected the induction of other defense response genes, particularly CaPR1, CaPR5 [25], and CaDEF1 [19].…”

“…Proline content and antioxidant enzymes diminish the risk of oxidative damage trigger by various stresses [ 27 , 62 ]. The content of proline as a regulator of C. acutatum in the non-transformed, pTRV2:00, and CaChiIII7 -silenced pepper plants was also measured.…”

“…The positive clones were grown on rifampicin, gentamicin, and kanamycin (RGK) media. A suspension culture with OD 600 = 1.0 was injected into the fully expanded cotyledonary leaves of pepper plants through a syringe without a needle [27,93]. Moreover, the negative control TRV2:00 (empty vector) and the positive control TRV2:CaPDS (phytoene desaturase) were also transformed.…”

“…Pepper genes that participate in cell death or the defense mechanism of plants are induced swiftly and distinctively by pathogen infection. The PCD or stress response genes include CaLRR51 (leucine-rich repeat protein) [ 18 ], CaDEF1 (defensin) [ 19 ], PFLP (plant ferredoxin-like protein) [ 20 ], CaSAR8 .2 [ 21 ], CaLOX1 (lipoxygenase) [ 22 ], CaMBL1 (mannose-binding lectin) [ 23 ], CaPO2 (peroxidase) [ 24 ], CaPR1 (pathogenesis-related protein 1) [ 25 ], CaPR10 [ 26 ], CaChiIV1, and CaChiVI2 (chitinase) [ 27 , 28 ].…”

The Arabidopsis SMALL AUXIN UP RNA32 Protein Regulates ABA-Mediated Responses to Drought Stress

“…Then, the recombinant plasmids were transformed into Agrobacterium tumefaciens strain GV3101. Agrobacterium-mediated transformation was performed using wild-type (WT) Arabidopsis by floral dip method (Zhang et al, 2006;Ali et al, 2020b). Transgenic plants were selected and then screened with 0.1% Basta for their ability to overexpress AtSAUR32.…”