Transcriptome pathways unique to dehydration tolerant relatives of modern wheat

Among abiotic stressors, drought is a major factor responsible for dramatic yield loss in agriculture. In order to reveal differences in global expression profiles of drought tolerant and sensitive wild emmer wheat genotypes, a previously deployed shock-like dehydration process was utilized to compare transcriptomes at two time points in root and leaf tissues using the Affymetrix GeneChip(R) Wheat Genome Array hybridization. The comparison of transcriptomes reveal several unique genes or expression patterns such as differential usage of IP(3)-dependent signal transduction pathways, ethylene- and abscisic acid (ABA)-dependent signaling, and preferential or faster induction of ABA-dependent transcription factors by the tolerant genotype that distinguish contrasting genotypes indicative of distinctive stress response pathways. The data also show that wild emmer wheat is capable of engaging known drought stress responsive mechanisms. The global comparison of transcriptomes in the absence of and after dehydration underlined the gene networks especially in root tissues that may have been lost in the selection processes generating modern bread wheats

Autophagy-related gene, TdAtg8, in wild emmer wheat plays a role in drought and osmotic stress response

An autophagy-related gene Atg8 was cloned for the first time from wild emmer wheat, named as TdAtg8, and its role on autophagy under abiotic stress conditions was investigated. Examination of TdAtg8 expression patterns indicated that Atg8 expression was strongly upregulated under drought stress, especially in the roots when compared to leaves. LysoTracker(®) red marker, utilized to observe autophagosomes, revealed that autophagy is constitutively active in Triticum dicoccoides. Moreover, autophagy was determined to be induced in plants exposed to osmotic stress when compared to plants grown under normal conditions. Functional studies were executed in yeast to confirm that the TdATG8 protein is functional, and showed that the TdAtg8 gene complements the atg8∆::kan MX yeast mutant strain grown under nitrogen deficiency. For further functional analysis, TdATG8 protein was expressed in yeast and analyzed using Western immunoblotting. Atg8-silenced plants were exposed to drought stress and chlorophyll and malondialdehyde (MDA) content measurements demonstrated that Atg8 plays a key role on drought stress tolerance. In addition, Atg8-silenced plants exposed to osmotic stress were found to have decreased Atg8 expression level in comparison to controls. Hence, Atg8 is a positive regulator in osmotic and drought stress response

Conserved microRNAs and their targets in model grass species Brachypodium distachyon

MicroRNAs are small, non-protein-coding RNAs playing regulatory functions in many organisms. Using computational approaches 26 new Brachypodium distachyon miRNAs belonging to 19 miRNA families were identified in expressed sequence tags (EST) and genomic survey sequence databases. EST revealed that predicted miRNAs are expressed in B. distachyon. Detailed nucleotide analyses showed that pre-miRNAs in B. distachyon are in the range of 63-180 nucleotides. Mature miRNAs located in the different positions of precursor RNAs are varied from 19 to 24 nucleotides in length. Quantifying RNAs using realtime PCR (qRT-PCR) analyses validated expression level differences of selected B. distachyon miRNAs. In this study, we detected that the expression level of some of the predicted miRNAs are distinct and some of them are similar in the leaf tissues. In addition, using these miRNAs as queries 27 potential target mRNAs were predicted in B. distachyon NCBI EST database and 246 target mRNA were predicted in NCBI protein-coding nucleotide (mRNA) database of all plant species. The majority of the target mRNAs encode transcription factors regulating plant development, morphology and flowering time. Other newly identified miRNAs target the mRNAs involving metabolic processes, signal transduction and stress response