title: Abiotic stresses modulate expression of major intrinsic proteins in barley (Hordeum vulgare).
abstract: In one of the most important crops, barley (Hordeum vulgare L.), gene expression and physiological roles of most major intrinsic proteins (MIPs) remained to be elucidated. Here we studied expression of five tonoplast intrinsic protein isoforms (HvTIP1;2, HvTIP2;1, HvTIP2;2, HvTIP2;3 and HvTIP4;1), a NOD26-like intrinsic protein (HvNIP2;1) and a plasma membrane intrinsic protein (HvPIP2;1) by using the quantitative real-time RT-PCR. Five-day-old seedlings were exposed to abiotic stresses (salt, heavy metals and nutrient deficiency), abscisic acid (ABA) and gibberellic acid (GA) for 24 h. Treatment with 100 mM NaCl, 0.1 mM ABA and 1 mM GA differentially regulated gene expression in roots and shoots. Nitrogen and prolonged P-deficiency downregulated expression of most MIP genes in roots. Intriguingly, gene expression was restored to the values in the control three days after nutrient supply was resumed. Heavy metals (0.2 mM each of Cd, Cu, Zn and Cr) downregulated the transcript levels by 60-80% in roots, whereas 0.2 mM Hg upregulated expressions of most genes in roots. This was accompanied by a 45% decrease in the rate of transpiration. In order to study the physiological role of the MIPs, cDNA of three genes (HvTIP2;1, HvTIP2;3 and HvNIP2;1) have been cloned and heterologous expression was performed in Xenopus laevis oocytes. Osmotic water permeability was determined by a swelling assay. However, no water uptake activity was observed for the three proteins. Hence, the possible physiological role of the proteins is discussed.
authors.affiliation: Cornell University, Robert Holley Center, USDA-ARS, Ithaca, New York 14853, USA. ayalewligaba@hotmail.com
authors.forename: Ayalew
authors.initials: A
authors.lastname: Ligaba
authors.forename: Maki
authors.initials: M
authors.lastname: Katsuhara
authors.forename: Mineo
authors.initials: M
authors.lastname: Shibasaka
authors.forename: Gemechis
authors.initials: G
authors.lastname: Djira
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects; D018076:DNA, Complementary / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D005875:Gibberellins / Q000494:pharmacology; D001467:Hordeum / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D019216:Metals, Heavy / Q000494:pharmacology; D009865:Oocytes; D009995:Osmosis / Q000187:drug effects; D010802:Phylogeny; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D018526:Plant Transpiration / Q000187:drug effects; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014982:Xenopus laevis
chemical_list: D018076:DNA, Complementary; D005875:Gibberellins; D008565:Membrane Proteins; D019216:Metals, Heavy; D010940:Plant Proteins; D011994:Recombinant Proteins; C077491:tonoplast intrinsic protein, plant; D012965:Sodium Chloride; D000040:Abscisic Acid; C007842:gibberellic acid