Seawater stress effects on mitochondrial ATP synthesis and membrane potential (ΔΨ) were investigated in germinating durum wheat seedlings under moderate (22% seawater osmolarity, –0.62 MPa) and severe (37% seawater osmolarity, –1.04 MPa) stress. To estimate the osmotic component of salt stress, mannitol solutions (0.25 and 0.42 m) iso-osmotic with the saline ones were used. Moderate stress intensity only delayed mean germination time (MGT), whereas higher seawater osmolarity reduced germination percentage as well. In contrast, Na+ and Cl– accumulation showed a sharp increase under moderate stress and only a small further increase under severe stress, which was more pronounced for Cl–. Only severe stress significantly damaged succinate-dependent oxidative phosphorylation, which may be related to the stress-induced alteration in inner mitochondrial membrane permeability, as indicated by changes in ΔΨ profiles. Proline-dependent oxidative phosphorylation, however, was inhibited under moderate stress. This suggests the occurrence of an adaptation mechanism leading to proline accumulation as an osmoprotectant. Moreover, both the osmotic and the toxic components of seawater stress were detrimental to oxidative phosphorylation. Damage to germination and MGT, in contrast, were mainly caused by osmotic stress. Therefore, mitochondrial function appears to be a more sensitive target of toxic stress than growth. In conclusion, the effects of seawater stress on mitochondrial ATP synthesis vary in relation to the substrate oxidised and stress level, inducing both adaptive responses and damage.

The gluten protein composition and expression level influence dough properties and are cultivar and environment dependent. To broaden the knowledge of the durum wheat gluten proteome, three cultivars were compared in two different growing seasons by a proteomic approach. Cultivar-specific and differentially expressed spots in the two years were identified by mass spectrometry. Significant differences were observed among the cultivars: Ofanto showed the lowest protein spot volumes in the high molecular weight (HMW) and low molecular weight (LMW) <35,000 regions and the highest in the LMW 48,000-35,000 region, Latino the lowest in the LMW 48,000-35,000 region, and Simeto an intermediate expression level in both LMW regions. In the warmer year the up-regulation of HMW glutenins, α-gliadins, and a globulin 3 protein and the down-expression of LMW glutenins and γ-gliadins were observed. Among the cultivars, Simeto showed the highest stability across the environments.

Environmental stress during grain filling may affect wheat protein composition, thus influencing its final quality. A proteomic approach was used to evaluate changes in storage protein composition under water stress of two Italian durum wheat (Triticum turgidum ssp. durum) cultivars, Ciccio and Svevo. The high-molecular-weight glutenin region increased progressively in both cultivars and under two water regimens. The L48-35 region, corresponding to low-molecular-weight (LMW) glutenin subunits, increased slightly during grain development and decreased under water stress in both cultivars. In particular, an s-type LMW related to superior technological quality was down-expressed in the early-mid period in Svevo and in the mid-late period in Ciccio. Finally, the L<35 region, corresponding to gliadin-like proteins, decreased slightly during grain development and increased under stress in both cultivars. Several α-gliadins, associated with immunological potential, increased their expression under water stress, especially in Svevo in the early-mid stage of grain filling.

The important role of plant mitochondria in the adaptation to environmental stresses at subcellular level has recently emerged. In particular, an important mitochondrial mechanism involved in the resistance to environmental stresses is the inhibition of proline oxidation. In order to study this physiological mechanism, we used both washed and purified durum wheat (Triticum durum) mitochondria (DWM) isolated from early seedlings germinated in two different NaCl solutions leading to either moderate or severe damage to growth. To assess the contribution of the osmotic component of stress, a parallel investigation was performed using hyperosmotic mannitol solutions.Comparison of the oxygen uptake rate in the course of proline oxidation, with that of the malate plus glutamate substrate pair and that of succinate showed that an early inhibition of proline oxidation occurs under stress. The drop of the proline‐dependent oxygen uptake rate was as a result of a heavy inhibition of proline dehydrogenase (ProDH); on the other hand, malate plus glutamate‐dependent and succinate‐dependent oxidations were less inhibited, being the maintenance of oxygen uptake rate not dependent on alternative oxidase (AOX) pathway; in fact, DWM‐AOX activity did not show any increase under our experimental stress conditions. The selective inhibition of proline oxidation should be considered a mitochondrial adaptation to stress rather than damage to mitochondrial oxidative properties. This result was achieved by means of a novel approach based on the comparison between oxygen uptake rates of washed and purified organelles.

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