Transgenerational analyses and transcript memory profiling of SKP1 gene expression after seed priming with IAA and GA3 shows positive modulation of terminal heat stress tolerance in bread wheat (Triticum aestivum L.)

Abstract

Obligate exposure to high temperatures during the anthesis of wheat is a reality and one of the major challenges in wheat breeding today. Seed priming is a valuable technology to increase seed vigour and stress resilience. Seed priming of wheat cv. HD2967 was carried out with two plant hormones, auxin (IAA) and gibberellins (GA3) and the primed plants were analyzed in two consecutive seasons in a field at two planting times. The main aim was to determine how these hormones modulate various pre-germinative metabolic pathways, which lead to enhanced stress tolerance and finally affect crop yield after a triggered high-temperature stress at the anthesis stage. At the molecular genetic level, transcriptional memory was analyzed by expression profiling of the SKP1(S-phase kinase protein1)gene, an essential component of the ubiquitin-proteasome system that is specifically involved in protein homeostasis and plant hormonal signaling. The results revealed that the grain yield at all sowing times was significantly increased by IAA and GA3 seed priming (50 mg/L) under high ambient temperature. The SKP1 transcript showed maximum induction in the P1-D, P2-D, and P2-N conditions in the flag leaf and ear head under heat stress. The SKP1 gene expression showed a higher correlation with chlorophyll content at the post-anthesis stage (S3) by SKP1-FL r = .92 and SKP1-EH r=0.85 (p < 0.01) and a strong positive correlation with S3 r = 0.77and NOGPH r=0.77 (p < 0.01). These results document the potential of this technology as an effective approach to cope with severe high-temperature stresses during grain filling in wheat cultivation. To the best of our knowledge, this is one of the first reports of IAA, GA3, in combination with heat priming of seeds and analyses in natural field conditions in wheat.