BSc -MSc

The study entitled “Unraveling the role of Piriformospora indica in combating high temperature stress and analysis of chlorophyll metabolism - related genes in Elettaria cardamomum Maton” was conducted at the Biotechnology and Bioinformatics Division, JNTBGRI, Palode and Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani during 2022-2023. The primary objective of the study was the expression profiling of chlorophyll metabolism - related genes responding to Piriformospora indica induced cardamom plants under high temperature stress and evaluation of chlorophyll and mineral content.
During the study, cardamom cultivar ICRI 5 was propagated under in vitro conditions using full strength MS medium supplemented with 1 mg l-1 BAP (for shoot induction) and basal MS liquid medium (for root induction). Co-cultivation of cardamom plantlets with P. indica maintained in Potato Dextrose Agar (PDA) and Potato Dextrose Broth (PDB) was achieved under in vitro as well as ex vitro conditions. Trypan blue in lactophenol staining results revealed the presence of chlamydospores and hyphae of P. indica inside root cortex of P. indica colonised plants. P. indica inoculated plants were exposed to various temperature treatments such as 25̊C, 30̊C, 35̊C and 40̊ C inside a growth chamber. Uninoculated plants at each of these temperatures served as control. Various phenotypic traits were investigated for 6 months at 30 day interval. RNA was isolated from the leaves of both inoculated and uninoculated plants at various temperatures. Real time PCR was done to profile the expression of chlorophyll metabolism related genes and sHSPs.
Our findings revealed that P. indica symbiosis in cardamom plants had increased plant height, leaf number, leaf length and leaf area at all stages of observation. In addition, the photosynthetic pigments and mineral contents of plants were significantly enhanced by the P. indica colonization. With respect to plant height (13.87cm,16.784cm, 25.95cm, 27.36cm 33.6cm, 36.76cm), leaf length (7.4cm,13.4cm, 19.2cm, 23.36cm, 26.26cm, 28.54cm), leaf area (8.52cm2, 14.04cm2, 18.62cm2, 21.68cm2,25.50cm2) and leaf number (5.6, 6.8, 7.8, 10.2, 11.2, 12.) P. indica colonized plants at 25°C recorded highest value. However in high temperature stressed plants, P. indica colonized plants at 35°C recorded highest values of plant height (13.186cm, 15.94cm, 24.08cm, 26.720cm, 32.24cm, 35.78cm), leaf length (7cm, 12.78cm, 17.30cm, 22.5cm, 24.18cm, 26.48cm), leaf area (7.94 cm2, 13.54cm2, 17.94cm2, 20.22cm2, 27.64cm2) and leaf number (5,6.2,7,8.2,10.2,11.8). P. indica colonised plants at 25°C reported highest total chlorophyll and mineral content.
The expression levels of chlorophyll metabolism related genes such as GLU TR, CAO and POR and sHSP genes were significantly upregulated in P. indica colonized plants . This improvement in the transcripts of chlorophyll metabolism related genes could be correlated with a significant increment in total chlorophyll content. GLU TR, CAO and POR showed the highest expression in P. indica colonized plants maintained at 25°C with a fold change of 3.31, 3.03 and 2.05 respectively. Among the high temperature stress treatments, P. indica colonized plants at 35̊C showed greater upregulation in the expression in chlorophyll metabolism related genes with a fold change of 2.67, 2.08, 1.73 for GLU TR, CAO and POR respectively. The highest level of small heat shock transcript accumulation was evident in P. indica colonized plants at 35̊C with a significant fold change of 1.93 and 1.84 for sHSP17.8 and sHSP 17.9 respectively.