Cytokinin seed priming mediated induction of terminal heat stress tolerance and expression profiling of SKP1 transcripts, a component of ubiquitin proteasome system in bread wheat (Triticum aestivum L.): a transgenerational analysis

The global increase in ambient temperature is a critical factor and is one of the most important abiotic constraints in wheat. Terminal heat stress or stress during grain-filling reduces photosynthesis through metabolic limitations and oxidative damage to chloroplasts there by leading to yield reductions. Cytokinins (CKs) play a key role in diverse developmental processes including modulation of plant heat stress response. To identify and assess the effects of cytokinin under high temperature, seeds of wheat cvHD2967 were primed with 50 mg/L Kinetin with and without additional heat priming at 42 degrees C. Primed seeds were raised in season in field for two continuous years and exposed to elevated temperature intermittently in an indigenously built heat trap chamber at anthesis for three consecutive days. Extensive phenotyping of a series of agronomic, biochemical and physiological parameters were recorded. To assess transgenerational affect of priming, in the next year, the primed harvested seeds were sown in two staggered timings in season and similar data collected. Correlational analysis showed positive correlation between chlorophyll index and grain traits (r = 0.866, 0.892; p < 0.001). Survival of plants under stress relies heavily on proteomic plasticity. Ubiquitin proteasome system (UPS) plays a major role in maintaining this plasticity by critical interaction with plant hormones including cytokinins. Transcript expression profiling of SKP1(S-phase kinase protein1), an essential component of SCF (SKP1-Cullin-F-Box) ubiquitin ligase, in the primed plants showed differential and positive induction indicating their involvement and reveals avenue for breeding heat tolerant wheat. The results document that seed priming with cytokinins can be utilized as an alternative strategy to ameliorate adverse effects of high temperature in wheat production towards sustainable crop productivity under changing climate scenario.