Gene expression and physiological responses to salinity and water stress of contrasting durum wheat genotypes

Abstract

Elucidating the relationships between gene expression and the physiological mechanisms remains a bottleneck in breeding for resistance to salinity and drought. This study related the expression of key target genes with the physiological performance of durum wheat under different combinations of salinity and irrigation. The candidate genes assayed included two encoding for the DREB (dehydration responsive element binding) transcription factors TaDREB1A and TaDREB2B, another two for the cytosolic and plastidic glutamine synthetase (TaGS1 and TaGS2), and one for the specific Na(+) /H(+) vacuolar antiporter (TaNHX1). Expression of these genes was related to growth and different trait indicators of nitrogen metabolism (nitrogen content, stable nitrogen isotope composition, and glutamine synthetase and nitrate reductase activities), photosynthetic carbon metabolism (stable carbon isotope composition and different gas exchange traits) and ion accumulation. Significant interaction between genotype and growing conditions occurred for growth, nitrogen content, and the expression of most genes. In general terms, higher expression of TaGS1, TaGS2, TaDREB2B, and to a lesser extent of TaNHX1 were associated with a better genotypic performance in growth, nitrogen, and carbon photosynthetic metabolism under salinity and water stress. However, TaDREB1A was increased in expression under stress compared with control conditions, with tolerant genotypes exhibiting lower expression than susceptible ones.

Interactive Effects of Elevated [CO2] and Water Stress on Physiological Traits and Gene Expression during Vegetative Growth in Four Durum Wheat Genotypes

“…N content was also diminished by severe water stress in Regallo, in agreement with previous studies in durum wheat (Yousfi et al, 2012, 2016). Chlorophyll content only increased under elevated [CO 2 ] in Mexa at the first sampling date, but the effect disappeared at the second sampling (Table 3).…”

“…It could also be caused by carbohydrate accumulation, which may lead to increases in the number of tillers (Stitt and Krapp, 1999). On the other hand, severe water stress constrained plant growth (dry matter and NDVI), in agreement with earlier studies in durum wheat (Erice et al, 2014; Nakhforoosh et al, 2015; Yousfi et al, 2016), with Ramirez and Burgos being the genotypes most affected. According to Marti et al (2007), we suggest that progressive water restriction during the vegetative stage constrained the photosynthetic area, which may cause negative effects on final biomass and yield.…”

“…However, projections of future climate change in the Iberian Peninsula predict major rainfall limitations and higher evapotranspiration during winter months (Russo et al, 2015) and therefore early-season drought is a matter of concern. In this context, we describe the effects of elevated [CO 2 ] and water stress during the first part of the growth cycle in four durum wheat genotypes on physiological traits and expression of nine genes that respond to changes in [CO 2 ] and water levels (Ali-Benali et al, 2005; Budak et al, 2013; Vicente et al, 2015b; Yousfi et al, 2016). The coordination of these parameters under the different combinations of factors is discussed.…”

“…Measurements were carried out using an elemental analyzer (Flash 1112 EA; ThermoFinnigan, Bremen, Germany) coupled with an isotope ratio mass spectrometer (Delta C IRMS; ThermoFinnigan), operating in continuous flow mode, at the Scientific Facilities of the University of Barcelona. As has been described previously (Bort et al, 2014; Yousfi et al, 2016), the 13 C/ 12 C ratio was expressed in δ notation: δ 13 C (‰) = [( 13 C/ 12 C) sample /( 13 C/ 12 C) standard − 1] × 1000. The standard refers to international secondary standards of known 13 C/ 12 C ratios (IAEA CH7 polyethylene foil, IAEA CH6 sucrose, and USGS 40 L-glutamic acid) calibrated against Vienna Pee Dee Belemnite calcium carbonate.…”

“…Liu et al (2016) reported a progressive inhibition of photosynthetic activity as water stress is more severe in field-grown bread wheat, probably due to non-stomatal limitations, which led to lower grain yields even at moderate water stress. Furthermore, water stress in wheat leads to complex changes in the expression of some genes, including those involved in photosynthesis, respiration, N metabolism, lipid metabolism, transcription factors, signal transducers, and synthesis of protective proteins (Habash et al, 2009, 2014; Budak et al, 2013; Yousfi et al, 2016). These changes in gene expression occurred mainly in the early phases of the stress (Habash et al, 2014).…”