Search

Functional genomic elements, including transposable elements, small RNAs and non-coding RNAs, are involved in regulation of gene expression in response to plant stress. To identify genomic elements that regulate dehydration and alkaline tolerance in Boea hygrometrica, a resurrection plant that inhabits drought and alkaline Karst areas, a genomic DNA library from B. hygrometrica was constructed and subsequently transformed into Arabidopsis using binary bacterial artificial chromosome (BIBAC) vectors. Transgenic lines were screened under osmotic and alkaline conditions, leading to the identification of Clone L1-4 that conferred osmotic and alkaline tolerance. Sequence analyses revealed that L1-4 contained a 49-kb retroelement fragment from B. hygrometrica, of which only a truncated sequence was present in L1-4 transgenic Arabidopsis plants. Additional subcloning revealed that activity resided in a 2-kb sequence, designated Osmotic and Alkaline Resistance 1 (OAR1). In addition, transgenic Arabidopsis lines carrying an OAR1-homologue also showed similar stress tolerance phenotypes. Physiological and molecular analyses demonstrated that OAR1-transgenic plants exhibited improved photochemical efficiency and membrane integrity and biomarker gene expression under both osmotic and alkaline stresses. Short transcripts that originated from OAR1 were increased under stress conditions in both B. hygrometrica and Arabidopsis carrying OAR1. The relative copy number of OAR1 was stable in transgenic Arabidopsis under stress but increased in B. hygrometrica. Taken together, our results indicated a potential role of OAR1 element in plant tolerance to osmotic and alkaline stresses, and verified the feasibility of the BIBAC transformation technique to identify functional genomic elements from physiological model species. [ABSTRACT FROM AUTHOR]

Abiotic stresses disrupt protein folding and induce endoplasmic reticulum (ER) stress, which in turn activates the unfolded protein response (UPR) to aid in the refolding or degradation of misfolded proteins. The phytohormone ABA regulates many aspects of plant development and plays a central role in the stress response; however, the role of ABA in transducing stress signals to activate the UPR has not been recognized. In this study, a gene encoding the maize ortholog of AtbZIP17, a transmembrane transcription factor functioning as an ER stress transducer, was identified from the MaizeGDB database, and designated ZmbZIP17. ZmbZIP17 was induced by both ABA and ER stress-eliciting agents such as dithiotreitol (DTT) and tunicamycin (TM). Transiently expressed yellow fluorescent protein (YFP)–ZmbZIP17 co-localized with the ER marker HDEL–mCherry under control conditions, but partially translocated into the nucleus upon TM treatment or removal of the transmembrane domain. TM-induced processing of ZmbZIP17 was confirmed by Western blot analysis. When overexpressed in Arabidopsis, ZmbZIP17 triggered ER stress response gene expression and tolerance to DTT and TM, elevated ABA-responsive gene expression and ABA sensitivity both pre- and post-germination. Additionally, ABA was found to induce ER stress response gene expression, alone or synergistically with ZmbZIP17, in the absence of DTT or TM; while ZmbZIP17 was capable of interacting with ABA-responsive cis-elements (ABREs) that exist in promoters of known ABA-responsive genes. Together, our results reveal a direct link between ER stress and ABA signaling pathways involving the ZmbZIP17 transcription factor. [ABSTRACT FROM PUBLISHER]

Functional genomic elements, including transposable elements, small RNAs and non-coding RNAs, are involved in regulation of gene expression in response to plant stress. To identify genomic elements that regulate dehydration and alkaline tolerance in Boea hygrometrica, a resurrection plant that inhabits drought and alkaline Karst areas, a genomic DNA library from B. hygrometrica was constructed and subsequently transformed into Arabidopsis using binary bacterial artificial chromosome (BIBAC) vectors. Transgenic lines were screened under osmotic and alkaline conditions, leading to the identification of Clone L1-4 that conferred osmotic and alkaline tolerance. Sequence analyses revealed that L1-4 contained a 49-kb retroelement fragment from B. hygrometrica, of which only a truncated sequence was present in L1-4 transgenic Arabidopsis plants. Additional subcloning revealed that activity resided in a 2-kb sequence, designated Osmotic and Alkaline Resistance 1 (OAR1). In addition, transgenic Arabidopsis lines carrying an OAR1-homologue also showed similar stress tolerance phenotypes. Physiological and molecular analyses demonstrated that OAR1-transgenic plants exhibited improved photochemical efficiency and membrane integrity and biomarker gene expression under both osmotic and alkaline stresses. Short transcripts that originated from OAR1 were increased under stress conditions in both B. hygrometrica and Arabidopsis carrying OAR1. The relative copy number of OAR1 was stable in transgenic Arabidopsis under stress but increased in B. hygrometrica. Taken together, our results indicated a potential role of OAR1 element in plant tolerance to osmotic and alkaline stresses, and verified the feasibility of the BIBAC transformation technique to identify functional genomic elements from physiological model species. [ABSTRACT FROM AUTHOR]