title: miR394 and LCR are involved in Arabidopsis salt and drought stress responses in an abscisic acid-dependent manner.
abstract: BACKGROUND
  MicroRNAs (miRNAs) are a class of short, endogenous non-coding small RNAs that have ability to base pair with their target mRNAs to induce their degradation in plants. miR394a/b are conserved small RNAs and its target gene LCR (LEAF CURLING RESPONSIVENESS) encodes an F-box protein (SKP1-Cullin/CDC53-F-box) but whether miR394a/b and its target gene LCR are involved in regulation of plant response to abscisic acid (ABA) and abiotic stresses is unknown.
  
  
  RESULTS
  Mature miR394 and precursor miR394a/b are shown to be slightly induced by ABA. By contrast, LCR expression is depressed by ABA. Analysis of LCR and its promoter (pLCR::GUS) revealed that LCR is expressed at all development stages. MIR394a/b over-expression (35S::MIR394a/b) and lcr (LCR loss of function) mutant plants are hypersensitive to salt stress, but LCR over-expressing (35S::m5LCR) plants display the salt-tolerant phenotype. Both 35S::MIR394a/b and lcr plants are highly tolerant to severe drought stress compared with wild-type, but 35S::m5LCR plants are susceptible to water deficiency. Over-expression of MIR394a/b led to ABA hypersensitivity and ABA-associated phenotypes, whereas 35S::m5LCR plants show ABA resistance phenotypes. Moreover, 35S::MIR394a/b plants accumulated higher levels of ABA-induced hydrogen peroxide and superoxide anion radicals than wild-type and 35S::m5LCR plants. Expressions of ABA- and stress-responsive genes, ABI3, ABI4, ABI5, ABF3, and ABF4 are up-regulated in MIR394a/b over-expressing plants but down-regulated in 35S::m5LCR plants. Over-expression of MIR394a in abi4-1 or abi5-1 background resulted in loss of ABA-sensitivity in 35S::MIR394a plants.
  
  
  CONCLUSIONS
  The silencing of LCR mRNA by miR394 is essential to maintain a certain phenotype favorable for the adaptive response to abiotic stresses. The contrasting phenotypes of salt and drought responses may be mediated by a functional balance between miR394 and LCR. If the balance is perturbed in case of the abiotic stress, an identical phenotype related to the stress response occurs, resulting in either ABA sensitive or insensitive response. Thus, miR394-regulated LCR abundance may allow plants to fine-tune their responses to ABA and abiotic stress.
authors: Jian Bo
authors: JB
authors: Song
authors: Shuai
authors: S
authors: Gao
authors: Di
authors: D
authors: Sun
authors: Hua
authors: H
authors: Li
authors: Xia Xia
authors: XX
authors: Shu
authors: Weigang No, 1, College of Life Science, Nanjing Agricultural University, Nanjing 210095, China. zmyang@njau.edu.cn.
authors: Zhi Min
authors: ZM
authors: Yang
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018548:Cotyledon / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D003890:Desiccation; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018525:Germination / Q000187:drug effects / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D054046:Plant Stomata / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological / Q000187:drug effects* / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; C579342:MIRN394 microRNA, Arabidopsis; D035683:MicroRNAs; D012965:Sodium Chloride; D000040:Abscisic Acid; D003577:Cytochrome P-450 Enzyme System; C434730:CYP86A8 protein, Arabidopsis