Effect of water stress on photosystem 2 in two wheat cultivars

Abstract

The effects of osmotic dehydration on the photochemical activity, gene transcription, and protein content of photosystem 2 (PS 2) in leaves of two wheat (Triticum aestivum L.) cultivars Miannnong No. 4 and No. 5 were studied. Roots of both cultivars were submerged into polyethylene glycol (PEG) solutions with an osmotic potential of -0.5 MPa for 0, 24, 48, and 72 h. Relative water content (RWC) decreased markedly after 48 and 72 h. Simultaneously, marked increase in electrolyte leakage, decrease in contents of chlorophylls (Chl) a and b, and inhibition in PS 2 activity were observed. Northern hybridization indicated that progressive water stress remarkably reduced contents of the chloroplast gene psbA and psbD and nuclear gene cab transcripts. Urea-SDS-PAGE and Western blotting analysis showed that the contents of major PS 2 proteins, including the D1 and D2 proteins in the PS 2 reaction centre (RC) and the light-harvesting Chl a/b-protein complex (LHC 2) in periphery, declined with increasing water stress. Miannong No. 5 had less destroyed plasma membranes and higher RWC, Chl contents, and PS 2 activity during water stress than Miannong No. 4, which suggested its better drought resistance. The significant difference in steady state contents of LHC 2 proteins of two cultivars can be mainly attributed to the marked difference in transcript level of cab gene, which indicated that LHC 2 proteins protect PS 2 RC.Additional key words: chlorophylls a and b, DCIP reduction, D1 and D2 proteins, electrolyte leakage of cell membrane, gene expression, LHC 2, Northern blot, polyacrylamide gel electrophoresis, Triticum aestivum, Western blot.

Alginate oligosaccharides enhanced Triticum aestivum L. tolerance to drought stress

“…If a plant is exposed to drought stress for a short period, Photosystem (PS) II will generate adaptation mechanism for preventing photoinhibition which is reflected by chlorophyll synthesis alteration [27]. Prolonged dehydration inhibits protein de novo synthesis and decreases gene transcriptions (such as psbA) [28]. In our results, exogenous AOS could induce LEA1 expression at early period to protect wheat from damage caused by drought stress.…”

Correlations between delayed fluorescence of chlorophyll, metabolism and yield of plants. II. Influence of moisture of leaf and temperature condition on delayed fluorescence of leaves

“…It is noteworthy that in case of interaction between the increased temperatures and the drought the structural organization and regular processes in the cells of plants were broken in more degree [3,4]. Simultaneously, in condition of the water loss of wheat leaves, the roots of which were submerged into polyethylene glycol solutions, an increase in electrolyte leakage, decrease in contents of chlorophylls a and b, major PSII proteins, including the D1 and D2 proteins in the PSII and the LHC2 and I, whole inhibition of PSII activity were obtained [5]. Northern hybridization showed that progressive water stress remarkably reduced contents of the chloroplast gene psbA and psbD and nuclear gene cab transcripts [5] and 62 genes differentially expressed under osmotic stress [6].…”

“…Simultaneously, in condition of the water loss of wheat leaves, the roots of which were submerged into polyethylene glycol solutions, an increase in electrolyte leakage, decrease in contents of chlorophylls a and b, major PSII proteins, including the D1 and D2 proteins in the PSII and the LHC2 and I, whole inhibition of PSII activity were obtained [5]. Northern hybridization showed that progressive water stress remarkably reduced contents of the chloroplast gene psbA and psbD and nuclear gene cab transcripts [5] and 62 genes differentially expressed under osmotic stress [6]. On the other hand, it was assumed that water stress had no effects on the primary photochemistry of PSII, but modified the PSII photochemistry in the light-adapted leaves and such modifications may be a mechanism to down-regulate the photosynthetic electron transport to match a decreased CO 2 assimilation [7].…”

Sugarcane Responses at Water Deficit Conditions

“…The gene expression pattern identified for this metabolism corroborates to physiological conditions and could be used as an indicative of drought sensitivity for this Brazilian sugarcane cultivar. In plants where the loss of water relative content was small, the photochemical activity was less affected by water stress, supporting the concept of plant productivity loss under drought conditions (Liu et al, 2006). On the other hand, in the tolerant sugarcane cultivar SP83-2847 the photosynthetic rate decreased under mild stress, but several genes related to photosynthesis were induced under this condition, probably because the stress was not strong enough to produce www.intechopen.com photoinhibition.…”