Isolation and characterization of HSP family gene from cardamom (elettaria cardamomum maton)

Abstract

The study entitled “Isolation and characterization of Hsp family gene from cardamom (Elettaria cardamomum Maton)” was conducted at the Biotechnology and Bioinformatics Division, KSCSTE - Jawaharlal Nehru Tropical Botanic Garden and Research Institute (JNTBGRI), Palode, Thiruvananthapuram, during 2019 – 2020. The primary objective of this study was to analyze differentially expressed genes belonging to small heat shock (sHsp) family under heat stress from cardamom. During the study, six month old cardamom plantlets were exposed to thermal stress by gradually increasing the temperature from 22 °C to 40 °C to understand the mode of expression of small heat shock protein (sHsp) transcripts namely sHsp 17.8, sHsp 17.9, sHsp 18.1 and sHsp 18.6. After attaining 40 °C, the heat stress treatment was continued for a period of 3 hrs and leaf tissues were collected at instants viz. 30 min, 1 hr, 2 hr and 3 hr intervals. Total RNA was isolated from control as well as treated samples and converted to cDNA. Real-Time PCR analysis was performed using gene specific primers designed from cardamom transcriptome data. The highest level of transcript accumulation was evident after the exposure of plants to thermal stress at 40 °C for 30 min. Among the four sHsps studied, sHsp 18.1 and sHsp 17.8 showed the highest expression at 30 min with a fold change of 5571 and 5000 respectively compared to the control. The two remaining sHsps also showed considerable upregulation during the initial period of heat stress. After 30 min, a sharp reduction in the expression of all sHsp transcripts has been observed. In addition to this, the overall transcript kinetics were different among the sHsp genes studied. These differentially expressed genes were isolated, purified and sequenced. Sequence analysis using various bioinformatics tools confirmed their identity as small heat shock proteins. Physico-chemical parameters as well as secondary structure were predicted using Protparam and PSIPRED respectively. In line with our results, it can be speculated that 17.8 and 18.1 sHsps could be used as potential biomarker candidates for screening tolerance to heat stress in cardamom. The findings obtained from this study can be used as a foundation for future lines of research related to rational improvement of cardamom against thermal stress.