PR-10, defensin and cold dehydrin genes are among those over expressed in Oxytropis (Fabaceae) species adapted to the arctic

Abstract

In many studied plants, typical responses to cold treatment include up-regulating the hydrophilic COR/LEA genes and down-regulating photosynthesis-related genes, carbohydrate metabolism, GDSL-motif lipase, hormone metabolism and oxidative regulation genes. However, next to nothing is known about gene expression in arctic plants, which are actually adapted to a harsh, cold environment. The molecular mechanisms behind the many specific adaptations of arctic plants, such as slow growth, well-developed root systems and short stature, are not well understood. In this study, we examine whole plantlet transcriptome differences between two arctic and two temperate Oxytropis (Fabaceae) species, grown under their respective controlled environmental conditions. Gene expression differences are analyzed using cDNA library subtraction followed by expressed sequence tags sequencing and annotation. Sequences from a total of nearly 2,000 clones cluster into 121 and 368 unique genes from the arctic and from the temperate plants, respectively. The predominant biological process for genes from the arctic-enriched library is “response to stimulus”. A concurrent overexpression of pathogenesis-related class 10 proteins (PR-10), plant defensin and cold dehydrin genes is a novel feature for species adapted to stressful growth environment. The temperate-enriched genes are involved in photosynthesis, translation and nucleosome assembly. Interestingly, both arctic and temperate-enriched libraries also contain genes involved in ribosome biogenesis and assembly, however of different types. Real-time reverse transcription PCR of cold dehydrin and two PR-10 genes, as well as the light harvesting complex b1 genes demonstrates that the gene expression is dependent on species and growth conditions.Electronic supplementary materialThe online version of this article (doi:10.1007/s10142-011-0223-6) contains supplementary material, which is available to authorized users.

The Pathogenesis Related Class 10 proteins in Plant Defense against Biotic and Abiotic Stresses

“…Moreover, PR-10 proteins are over expressed in Oxytopis (Fabaceae) species adapted to the Arctic as opposed to temperate species [92]. In a study by Vaas et al [93], overexpression of PR-10a in suspension cultures of Solanum tuberosum causes an enhanced osmotic tolerance, which in turn leads to enhanced ability for cryo preservation. Abiotic stress-induced Zea mays PR-10 genes (ZmPR-10 and ZmPR-10.1) were also up-regulated following infection with pathogenic bacteria Erwinia stewartii and fungus Aspergillus flavus in young maize leaves and immature kernels, respectively [9].…”

The Y-segment of novel cold dehydrin genes is conserved and codons in the PR-10 genes are under positive selection in Oxytropis (Fabaceae) from contrasting climates

“…Nevertheless, arctic plants serve important purposes, such as feeding mammalian herbivores and insect pollinators. Using library subtraction and clone sequencing (ESTs), we recently reported that plantlets of two arctic Oxytropis species show a distinctive transcriptome compared to two temperate relative species (Archambault and Strömvik 2011). Arctic plantlets preferentially express response to stimulus (especially PR-10, cold dehydrins and defensin gene families) and ribosome biogenesis genes, whereas temperate plantlets express photosynthesis (including lhcbI and lhcaIII genes), ribosome biogenesis and translation and nucleosome assembly genes, as well as a few response to stimulus genes.…”

“…We have previously shown that plantlet transcriptomes from temperate Oxytropis plantlets are mainly enriched in transcripts of the "Photosynthesis" category (Archambault and Strömvik 2011). Proteins of the light-harvesting complex, for instance LHCBI (also called CAB8 in Pisum sativum) and LHCAIII (light-harvesting chlorophyll-a/b protein of photosystem I, type III) that function as a light receptor to capture and deliver excitation energy to photosystems (Timko et al 1985), are among the genes most prominently overrepresented in the temperate plantlet transcriptome.…”

“…These genes are far better known for their allergenic eVect in human (Berkner et al 2009), while their functions in plants remain somewhat elusive. Cold dehydrins are other genes of the "Response to stimulus" category that we have previously shown to be strongly overrepresented in arctic Oxytropis plantlet transcriptomes (Archambault and Strömvik 2011). Proteins of this gene family are small hydrophilic, heat-stable proteins known as LEA D-11 family (reviewed in Battaglia et al 2008).…”

“…The diVerential expression of many diVerent gene copies of the stimulus response category, belonging to many diVerent gene families was an important Wnding from our initial comparative transcriptome study (Archambault and Strömvik 2011). The Gene Balance Hypothesis predicts that genes retained (not silenced) following tandem duplication are not dosage-sensitive and tend to belong to response to stimulus functions or to be membrane proteins (reviewed in Edger and Pires 2009;Freeling 2009).…”