RAV transcription factor regulatory function in response to salt stress in two Iranian wheat landraces

Amongst the transcription factor groups, the AP2/ERF (Apetala2/Ethylene Response Factor) superfamily is one of the main groups in plants and plays an essential role in tolerating abiotic and biotic stresses. The AP2/ERF superfamily consists of ERF, AP2, RAV, and Soloist families based on the AP2 domain number. The RAV (Related to ABI3/VP1) family members have been revealed to be stimulate by a number of biotic and abiotic environmental incentives; including pathogen infection, salicylic acid, osmotic stress, cold, high salinity, wounding, and exogenous hormone application. However, limited data are available on the contributions of RAV transcription factors in wheat (Triticum aestivum L.). In the present study, a total of 26 RAV genes were identified in wheat from a genome-wide search against the latest wheat genome data. Phylogenetic and sequence alignment analyses divided the wheat RAV genes into 4 clusters, I, II, III and IV. Chromosomal distribution, gene structure and motif composition were subsequently investigated. The 26 TaRAV genes were unevenly distributed on 21 chromosomes. After cloning and sequencing of 7 TaRAVs candidate genes the expression levels of two TaRAVs, TaRAV4 and TaRAV5, were validated through qPCR analyses in two salt-tolerant Iranian landraces of wheat. Our results showed that the TaRAV4 and TaRAV5 were co-expressed in wheat tissues and were highly correlated to salt tolerance indices such as the K⁺/Na⁺ ratio. Protein interaction revealed that the TaRAV4 and TaRAV5 were related to vital proteins such as PK4 and PP2C, and MYB and Zinc finger transcription factors, and Gigantea proteins. This study improved our knowledge of the RAV gene family function in wheat and the probable role of RAVs in salt tolerance mechanisms to improve crop production under changing environments. Also, the two relatively salt-tolerant landraces of wheat that were examined in this study could be suitable candidates for future breeding studies.