The rehydration transcriptome of the desiccation-tolerant bryophyte Tortula ruralis: transcript classification and analysis

Abstract

Background: The cellular response of plants to water-deficits has both economic and evolutionary importance directly affecting plant productivity in agriculture and plant survival in the natural environment. Genes induced by water-deficit stress have been successfully enumerated in plants that are relatively sensitive to cellular dehydration, however we have little knowledge as to the adaptive role of these genes in establishing tolerance to water loss at the cellular level. Our approach to address this problem has been to investigate the genetic responses of plants that are capable of tolerating extremes of dehydration, in particular the desiccation-tolerant bryophyte, Tortula ruralis. To establish a sound basis for characterizing the Tortula genome in regards to desiccation tolerance, we analyzed 10,368 expressed sequence tags (ESTs) from rehydrated rapiddried Tortula gametophytes, a stage previously determined to exhibit the maximum stress induced change in gene expression.

A Systems‐Based Molecular Biology Analysis of Resurrection Plants for Crop and Forage Improvement in Arid Environments

“…More than a decade later, while much of the signal transduction pathway in plant drought stress response has been elucidated in model plants such as Arabidopsis, corresponding information is still fragmentary in resurrection plants. The scarcity of information may be a consequence of the fact that of the 300-400 known resurrection plants, the molecular genetic basis of desiccation tolerance has been studied in relatively few species, namely, the mosses S. lepidophylla [60] and T. ruralis [61], the monocots S. stapfianus [62], X. viscosa [22], and X. humilis [48], and the dicot C. plantagineum [13]. In C. plantagineum, the synthesis of phospholipid-based signaling molecules is known as one of the earliest events in the perception of water stress.…”

“…Phosphorylation is believed to be required for the function of these proteins that is proposed to protect the catalytic activities of enzymes by altering the stability or specificity of proteinprotein interactions [77]. LEAs may also play a role in recovery during rehydration in T. ruralis [61]. It has been proposed that in rehydrating T. ruralis gametophytes, LEA proteins may stabilize membranes or perhaps function in the transport of lipids for reconstitution of damaged membranes [78].…”

“…Recently, changes in the leaf proteomes of resurrection plants during desiccation were examined in X. viscose [28] and in B. hygrometrica [85] using quantitative 2D SDS-PAGE analysis. Several novel gene products, not previously isolated in transcriptomic studies, were identified as being upregulated during [61,86] T. ruralis cDNA libraries enriched with ESTs from slow drying and rehydrating gametophytes revealed genes involved in metabolic recovery, signaling, proteosomal processing, and splicing [94] Lycophyte Selaginella lepidophylla EST library corresponding to approximately 800 genes compared to 1300 genes from desiccation-sensitive S. moellendorfii. Genes identified that are involved in transport, cytoskeleton, phenylpropanoid biosynthesis, LEA proteins, ELIPs, and HSPs [60] Angiosperm S. stapfianus 144 cDNA upregulated genes in dried leaves; mostly LEA genes, defense, and detoxification genes [95] X. humilis Normalized cDNA library (about 10 000 clones) from dried roots and leaves containing 424 sequenced and arrayed cDNA.…”

“…For both X. viscosa [28] and B. hygroscopica [85], this has resulted in low success rate ($30%) in protein identification when searching against the NCBI nonredundant database. Although large EST collections (containing more than 10 000 ESTs and representing several thousand genes) are available for T. ruralis [86] and X. humilis [48], this number is probably still too low to increase the protein identification success rate significantly for proteomics study. For that, a much larger EST collection would be needed.…”

Functional Genomics of Drought Tolerance in Crops: Engineering Transcriptional Regulators and Pathways

“…Plant breeders have recognized that genotypes that are resistant to oxidative stress are also resistant to drought and hightemperature stress [67], providing a correlating evidence for the importance of oxidative stress tolerance. Functional genomic studies on naturally dehydration tolerant species and the effects of simultaneous application of drought and high temperature on plants have revealed key roles for antioxidant enzymes in both drought and high-temperature stress tolerance [68,69]. Future work is needed to identify differences, similarities, and overlaps between signaling pathways leading to high-temperature stress and those leading to drought tolerance.…”