Transcript profiling identifies novel transcripts with unknown functions as primary response components to osmotic stress in wheat (Triticum aestivum L.)

Abstract

Osmotic stress induced by dehydration and salinity, is among the major abiotic stresses that adversely impacts crop productivity and plants often display cultivar-dependent response against osmotic imbalance. To better understand the molecular mechanisms underlying differential responses to dehydration, transcriptome changes of two contrasting wheat (Triticum aestivum L.) cultivars were evaluated in plants grown under unfavorable osmotic conditions. A total of 107 non-redundant transcripts were identified. Of these, most had unknown functions (31; ~30 %) signifying the existence of putative stress-specific genes in wheat, reported here for the first time. Upon comparing with previous transcriptomic studies, 43 (40 %) of the osmotically-responsive transcripts were found not to be documented. These new transcripts may therefore signify unexplored gene sources for specific responses towards short-term osmotic stress in wheat. Through macroarray analysis, 69 (~64 %) transcripts were found to be differentially expressed (≥3-fold) and expression of 14 transcripts (with known or unknown functions) was further confirmed by quantitative real time PCR. Expression analysis of the seven unknown transcripts also revealed their tissue- and stress-specific regulation. Comparative in silico mapping of these 107 wheat transcripts against available mapping data for rice (40; ~37 %), maize (34; ~32 %), and sorghum (33; ~31 %) revealed presence of wheat orthologous sequences in these cereal crops. This study provides an interesting account on several novel genes, besides those with known functions, which may regulate stress response dynamics and thus, may be used as potential candidates to improve stress adaptability through genetic and molecular studies.