AUTHOR=Ali Muhammad , Muhammad Izhar , ul Haq Saeed , Alam Mukhtar , Khattak Abdul Mateen , Akhtar Kashif , Ullah Hidayat , Khan Abid , Lu Gang , Gong Zhen-Hui 

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

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.00219

DOI=10.3389/fpls.2020.00219

ISSN=1664-462X

ABSTRACT=<p>Extreme environmental conditions seriously affect crop growth and development, resulting in substantial reduction in yield and quality. However, chitin-binding proteins (CBP) family member <italic>CaChiVI2</italic> 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 <italic>CaChiVI2</italic> (Capana08g001237) gene of pepper (<italic>Capsicum annuum</italic> L.) had a role in resistance to heat stress and physiological processes. The full-length open-reading frame (ORF) of <italic>CaChiVI2</italic> (606-bp, encoding 201-amino acids), was cloned into TRV2:<italic>CaChiVI2</italic> vector for silencing. The <italic>CaChiVI2</italic> 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 <italic>CaChiVI2</italic> in pepper resulted in increased susceptibility to heat and <italic>Phytophthora capsici</italic> infection. This was evident from the severe symptoms on leaves, the increase in superoxide (O<sub>2</sub><sup>–</sup>) and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) 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 <italic>CaChiIV2</italic>-overexpression in <italic>Arabidopsis thaliana</italic> showed mild heat and drought stress symptoms and increased transcript level of a defense-related gene (<italic>AtHSA32</italic>), indicating its role in the co-regulation network of the plant. The <italic>CaChiVI2</italic>-overexpressed plants also showed a decrease in MDA contents and an increase in antioxidant enzyme activity and proline accumulation. In conclusion, the results suggest that <italic>CaChiVI2</italic> gene plays a decisive role in heat and drought stress tolerance, as well as, provides resistance against <italic>P. capsici</italic> 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.</p>