Effect of high temperature on photosynthetic pigment accumulation, cell viability, and synthesis of heat shock proteins in some cultivars of triticum aestivum L. and triticum durum desf.

In this research, the effects of different temperature treatments on cell viability andphotosynthetic pigment accumulation of 16 bread (Triticum aestivum L.) and 14 durum(Triticum durum Desf.) wheat cultivars at early seedling stage were investigated. Inaddition, the diversity in two-dimensional (2-D) electrophoretic profiles of solubleproteins extracted from some thermotolerant and thermosensitive wheat cultivarssubjected to different temperature treatments was detected.In cell viability [2,3,5-triphenyltetrazolium chloride (TTC) reduction test] test,six-day-old seedlings of bread and durum wheat cultivars grown at 25ºC were subjectedto acclimation (37ºC, 24 h) and acclimation followed by 50ºC for 1 h treatments. TTCreduction was significantly decreased at acclimation followed by 50ºC for 1 h comparedto acclimation treatment (P<0.05). The significant differences among thermal tolerancelevels of cultivars were determined using this test. It was determined that bread wheatcultivar Basribey-95 (76.33%) has highest thermal tolerance, while bread wheat cultivarSönmez-2001 (7.91%) has lowest thermal tolerance in TTC test conducted in injuredprimary leaf tissues. In addition, the thermal tolerance values (%) of some bread(Basribey-95, Gerek-79, kizce-96, Bezostaya-1, Ceyhan-99, Gönen-98 and Gün-91) anddurum (Amanos-97, Ankara-98, Ege-88, Fuatbey-2000 and Çakmak-79) wheat cultivarswere found higher than average (30.86%) of thermal tolerances of all cultivars.In photosynthetic pigment accumulation test, five-day-old etiolated seedlings of breadand durum wheat cultivars were subjected to control (25ºC, 24 h), acclimation (37ºC, 24h), and acclimation followed by heat shock (37ºC, 24 h→50ºC, 1 h) treatments.Following temperature treatments at dark, the pigmentation of total chlorophylls (Chla+b) and carotenoids was determined in seedlings exposed to continuous light at 25ºCfor 24 h. The Chl a+b accumulation in bread and durum wheat cultivars was significantlydecreased with increasing temperature (P<0.05). At 37ºC/25ºC ratio (%), the decrementin Chl a+b accumulation was ranged from 15.37% (Ceyhan-99) to 50.73% ( kizce-96) inbread wheat cultivars, while this decrement was ranged from 22.23% (Gediz-75) to61.79% (Kızıltan-91) in durum wheat cultivars. At 37→50ºC/25ºC, the decrement in Chla+b accumulation was ranged from 32.13% (Gönen-98) to 60.06% (Cumhuriyet-75) inbread wheat cultivars, while this decrement was ranged from 45.19% (Ege-88) to 67.14%(Ankara-98) in durum wheat cultivars. Interestingly, bread and durum wheat cultivarsshowed similar distribution at below and above of means of all cultivars at 37ºC/25ºC(32.44%) and at 37→50ºC/25ºC (48.40%) ratios with respect to decrements in Chl a+baccumulation. The pigmentation of carotenoids in some cultivars was decreased at only atemperature compared to control, while it was significantly decreased at temperaturetreatments compared to control in some cultivars. In contrast, the accumulation ofcarotenoids was not affected by high temperature in some cultivars. In general, thechlorophyll/carotenoid ratio was progressively decreased with increasing temperature. Ingeneral, the decrement (%) in chlorophyll/carotenoid ratio was found lower in breadwheat cultivars than durum wheat cultivars at 37ºC/25ºC and 37→50ºC/25ºC ratios.In protein analysis, thermotolerant bread (Gönen-98) and durum (Ege-88) wheat cultivarsand thermosensitive bread (Cumhuriyet-75) and durum (Ankara-98) wheat cultivars wereselected based on decrement in accumulation of total chlorophylls at 37→50ºC/25ºCratio. Five-day-old seedlings of wheat cultivars were subjected to different temperaturetreatments [25ºC (24 h), 37ºC (24 h) and 37ºC (24 h)→50ºC (1 h)] and then, the totalsoluble proteins extracted from primary leaf tissues were analyzed by two-dimensional(2-D) electrophoresis (SDS-PAGE) followed by silver staining. Interestingly, all of thedisappeared, newly synthesized and/or markedly increased or decreased proteins were inlow molecular weights (16.1-24.0 kDa) and generally acidic character (pI 4.8-6.9). Fournormal cellular proteins with molecular weight of 22.9 kDa (pI 6.4) in cv. Gönen-98, 16.2kDa (pI 6.0) in cv. Ege-88, and 20.1 and 20.7 kDa (pI 4.8) in cv. Ankara-98 weredisappeared at both high temperature treatments compared to control. In addition, twoproteins (23.0 kDa, pI 6.4 and 23.8 kDa, pI 6.4) in Ankara-98 cultivar were disappearedat only 37→50ºC compared to control treatment. On the other hand, 16 heat shockproteins (HSPs) (18.0-23.6 kDa, pI 5.4-7.8) in cv. Gönen-98, 11 HSPs (17.7-22.9 kDa, pI6.0-7.1) in cv. Cumhuriyet-75, 14 HSPs in cv. Ege-88 (18.3-22.9 kDa, pI 6.0-7.8) and 8HSPs (18.0-22.9 kDa, pI 6.0-6.4) in cv. Ankara-98 were newly synthesized at 37ºCand/or 37→50ºC treatments compared to control. The amounts of three normal cellularproteins (16.1, 16.1, and 23.0 kDa; pI 6.3, 6.4, and 6.6) determined in control treatmentwere markedly decreased at high temperature treatments, while 23.0 kDa (pI 6.4) proteinamong these proteins was disappeared at only 37→50ºC treatment in cv. Ankara-98.However, the amount of 23.6 kDa (pI 6.7) protein was markedly increased at hightemperature treatments in cv. Gönen-98. It may suggest that these proteins at differentsynthesis states play an important role in acquiring of thermal tolerance.2006, 102Keywords: Triticum L. cultivars, heat stress, cell viability, photosynthetic pigmentation,heat shock proteins, thermal tolerance