Submitted to: Journal of Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/30/2014
Publication Date: 6/6/2014
Citation: Reddy, S., Liu, S., Xue, Q., Payton, P.R., Finlayson, S., Mahan, J.R., Akhunova, A., Holalu, S., Lu, N. 2014. Physiology and transcriptomics of water-deficit stress responses in wheat cultivars TAM 111 and TAM 112. Journal of Plant Physiology. 171(14) 1289-1298. Interpretive Summary: Hard red winter wheat is a major crop in the western US. Wheat is grown under a wide range of water inputs. In some regions it is grown under rainfed conditions and in other it can be irrigated. The is great interest in wheat varieties that can produce more yield on less water. The varieties TAM111 and TAM112 are widely grown across the wheat region. It is generally noted that TAM111 has higher yields that TAM112 under high water but TAM112 is the higher yielder under water deficits. In this study we compared changes in gene expression between the two varieties under full and deficit irrigation. The two varieties showed large differences in gene expression responses to water deficits suggesting that TAM112 and TAM111 respond differently to stress on whole plant and gene expression levels. This work suggests that hormone changes probably play an important role in the different responses.
Technical Abstract: Hard red winter wheat crops on the U.S. Southern Great Plains often experience moderate to severe drought stress, especially during the grain filling stage, resulting in significant yield losses. Among popular commercial varieties, TAM 111 and TAM 112 showed a superior adaptation to water-deficit conditions and as such are widely cultivated in the region. Extensive yield trials on these two cultivars suggested distinct adaptation mechanisms under variable water-deficit conditions. Nevertheless, the mechanistic basis of their adaptation remains unknown. The objectives of this study were to elucidate the physiological and molecular basis of water-deficit stress responses in TAM 111 and TAM 112. A comprehensive greenhouse study was conducted to understand the physiological and transcriptomic responses to water-deficit conditions. TAM 112 showed increased biomass, higher cumulative transpiration, higher grain yield, but decreased leaf-level photosynthesis under water-deficit conditions compared to TAM 111. Transcriptomic data indicated that sustained water-deficit conditions during the grain filling stage altered more transcripts in TAM 112 compared to TAM 111. Functional classification of the differentially expressed transcripts suggested that TAM 112 suppressed the transcripts associated with photosynthesis, and elevated expression of transcripts mediating phytohormone metabolism, signaling, and other dehydration responses. Significantly higher abscisic acid levels were detected in TAM 112 compared to TAM 111 under sustained water-deficit conditions at the grain filling stage. These results shed light on potential mechanisms and candidate genes plausibly involved in adaptation to water-deficit conditions in leading TAM wheat cultivars and serve as vital resources for molecular breeding.