Gradual Soil Water Depletion Results in Reversible Changes of Gene Expression, Protein Profiles, Ecophysiology, and Growth Performance in Populus euphratica, a Poplar Growing in Arid Regions

Abstract

The responses of Populus euphratica Oliv. plants to soil water deficit were assessed by analyzing gene expression, protein profiles, and several plant performance criteria to understand the acclimation of plants to soil water deficit. Young, vegetatively propagated plants originating from an arid, saline field site were submitted to a gradually increasing water deficit for 4 weeks in a greenhouse and were allowed to recover for 10 d after full reirrigation. Time-dependent changes and intensity of the perturbations induced in shoot and root growth, xylem anatomy, gas exchange, and water status were recorded. The expression profiles of approximately 6,340 genes and of proteins and metabolites (pigments, soluble carbohydrates, and oxidative compounds) were also recorded in mature leaves and in roots (gene expression only) at four stress levels and after recovery. Drought successively induced shoot growth cessation, stomatal closure, moderate increases in oxidative stressrelated compounds, loss of CO 2 assimilation, and root growth reduction. These effects were almost fully reversible, indicating that acclimation was dominant over injury. The physiological responses were paralleled by fully reversible transcriptional changes, including only 1.5% of the genes on the array. Protein profiles displayed greater changes than transcript levels. Among the identified proteins for which expressed sequence tags were present on the array, no correlation was found between transcript and protein abundance. Acclimation to water deficit involves the regulation of different networks of genes in roots and shoots. Such diverse requirements for protecting and maintaining the function of different plant organs may render plant engineering or breeding toward improved drought tolerance more complex than previously anticipated.

Linking the Salt Transcriptome with Physiological Responses of a Salt-Resistant Populus Species as a Strategy to Identify Genes Important for Stress Acclimation

“…The time courses observed here suggest a protective function of dehydrins against ionic disorders (Mouillon et al, 2008), whereas the delayed activation of osmotins, another class of well-known stress-activated genes (Shinozaki and Yamaguchi-Shinozaki, 2007), indicates that these proteins must be involved in helping the plant to cope with life at a new level of cellular homeostasis. Surprisingly, Suc synthase was also salt responsive in both roots and leaves, but its transcript levels decreased under stress (Gu et al, 2004;Bogeat-Triboulot et al, 2007; this study). In contrast, its homolog AtSUS1 increases under stress (Ma et al, 2006).…”

DNA methylation and histone acetylation: genotypic variations in hybrid poplars, impact of water deficit and relationships with productivity

“…While poplar genotypes showed reduced growth in water deficit conditions, a significant genotype effect was observed for DNA methylation variations. This suggests that DNA methylation could participate to the fine-tuning of the reported control of gene expression in poplar during water stress (Plomion et al, 2006;Bogeat-Triboulot et al, 2007) including genotypespecific differences (Bonhomme et al, 2009). A complementary study should be done on the same plant material to confirm this hypothesis.…”

“…Thus, Ψ pd is one of the last parameters to be affected during an increasing water deficit (Bogeat-Triboulot et al, 2007). As the growth of aerial parts is the most sensitive parameter to water deficit, we assessed the impact of the moderate water deficit on morphological traits.…”

The mutual responses of higher plants to environment: Physiological and microbiological aspects

“…Plant production realization is obtained eventually through physiological pathways at least at the level of individual and community [102][103][104][105][106][107][108][109]120,[130][131][132][133][134][135][136][137][138][139][140]. One molecule or cell cannot produce any economic effect in field [22,23,77,78,117].…”

“…So, different soil water supply will result in quite different physiological pathways, which directly determine the ability for plants to make photosynthetic products. Water deficits in soil environment also influence solute transport (ion and nutrient uptake of plants) to larger extent, which effects on photosynthetic reactions in plant chloroplasts in many ways [117,120,131,135,[139][140][141][142][143][144][145][146][147]. This is the reason that ion homeostasis and redox state have been brought to attention [4][5][6][7][21][22][23][24][25][26][27][28][29][111][112][113][114][115][116][117][118][119].…”