Heat shock protein gene identified from Agave sisalana ( As HSP70) confers heat stress tolerance in transgenic cotton ( Gossypium hirsutum )

Genetic improvement of local cotton for tolerance against heat and other abiotic stresses is urgently needed due to climatic changes. Agrobacterium mediated transformation of G. hirsutum was done with heat shock protein gene (AsHSP70) and plants were analyzed for transgene expression at molecular, physiological and biochemical levels under heat stress. Genetic transformation revealed 1.9 % transformation efficiency. PCR amplified 1800 bp fragment of AsHSP70 in genomic DNA of transgenic plants. Polyamine oxidase induced the relative expression of AsHSP70 from 1.02 to 9.58 in transgenic plants as the duration of heat stress was increased. Expression of AsHSP70 was relatively higher in the leaves of transgenic plant as compared to root and stem under combined stress of heat/drought. Cell electrolyte leakage was 39.83 μS cm−1 and 63.43 μS cm−1 in transgenic and control plants respectively. Relative conductivity (4.05 %) was correlated with the membrane stability index (MSI) (97.19 %) in transgenic plants while it is 7.28 % when MSI is 90.19 % in control plants. Membrane injury was 19–52 % in control and 15.6–29 % in transgenic plants over the time of exposure to heat stress. Significant variation in chlorophyll, proline and soluble sugar content was observed in transgenic plants as compared to controls. Performance of transgenic plants was better for boll formation in the field. Single copy of transgene was detected in T1 progeny. Hence, transgenic cotton plants are tolerating heat and other abiotic stresses at physiological and biochemical levels. Single analyses of progeny may lead the selection of pure heat tolerant lines to be used in breeding program for cotton improvement under heat stress.