Photosynthetic Acclimation Is Reflected in Specific Patterns of Gene Expression in Drought-Stressed Loblolly Pine  

Abstract

Because the product of a single gene can influence many aspects of plant growth and development, it is necessary to understand how gene products act in concert and upon each other to effect adaptive changes to stressful conditions. We conducted experiments to improve our understanding of the responses of loblolly pine (Pinus taeda) to drought stress. Water was withheld from rooted plantlets of to a measured water potential of Ϫ1 MPa for mild stress and Ϫ1.5 MPa for severe stress. Net photosynthesis was measured for each level of stress. RNA was isolated from needles and used in hybridizations against a microarray consisting of 2,173 cDNA clones from five pine expressed sequence tag libraries. Gene expression was estimated using a two-stage mixed linear model. Subsequently, data mining via inductive logic programming identified rules (relationships) among gene expression, treatments, and functional categories. Changes in RNA transcript profiles of loblolly pine due to drought stress were correlated with physiological data reflecting photosynthetic acclimation to mild stress or photosynthetic failure during severe stress. Analysis of transcript profiles indicated that there are distinct patterns of expression related to the two levels of stress. Genes encoding heat shock proteins, late embryogenic-abundant proteins, enzymes from the aromatic acid and flavonoid biosynthetic pathways, and from carbon metabolism showed distinctive responses associated with acclimation. Five genes shown to have different transcript levels in response to either mild or severe stress were chosen for further analysis using real-time polymerase chain reaction. The real-time polymerase chain reaction results were in good agreement with those obtained on microarrays.

Gene expression changes in response to drought stress in Ilex paraguariensis leaves

“…Chorismate is the final product of the shikimate pathway and is the initiator metabolite for the synthesis of aromatic amino acids and secondary metabolites derived from these amino acids, including auxins, salicylates, antimicrobial alkaloids, flavonoids, and polyphenolic compounds produced in response to environmental signals as part of a general defence response (Less et al, 2010). The overexpression of genes encoding aromatic amino acids may be related to the protective role of flavonoids during photosynthetic acclimation under moderate water stress (Watkinson et al, 2003). Our results also showed an increased expression of the gene encoding metallothionein type 2 protein (MT) in response to stress severity.…”

Interactive effects of drought and pathogens in forest trees

“…Signalling pathways and genes involved in resistance to pathogens have been unravelled, first in model plants [54,208] and increasingly in many other species, including trees [9,68,141]. The molecular basis of plant response to abiotic stresses has also been extensively studied [213,219,224]. A number of studies provide some evidence of common mechanisms in response to a variety of stresses [108].…”

Characterization of Transformed Arabidopsis with Altered Alternative Oxidase Levels and Analysis of Effects on Reactive Oxygen Species in Tissue

“…[series entry] GSE2406). To distinguish differences in transcript levels, a two-step mixedmodel ANOVA procedure (Wolfinger et al, 2001; see discussion in Watkinson et al, 2003) adapted specifically for Affymetrix arrays (Chu et al, 2002) was used that allows determination of meaningful changes in gene expression based on statistical significance rather than using cutoff values of expression level fold changes. Data from the Affymetrix software .CEL files (signal intensity for each probe cell) for each array were log 2 -transformed, and then, in the first ANOVA step of the mixed model, were scaled and normalized to each other.…”