ABA is required for Leptosphaeria maculans resistance via ABI1- and ABI4-dependent signaling.
Abscisic acid (ABA) is a defense hormone with influence on callose-dependent and -independent resistance against Leptosphaeria maculans acting in the RLMcol pathway. ABA-deficient and -insensitive mutants in Ler-0 background (abal-3 and abil-1) displayed susceptibility to L. maculans, along with a significantly decreased level of callose depositions, whereas abi2-1 and abi3-1 remained resistant, together with the abi5-1 mutant of Ws-0 background. Suppressor mutants of abil-1 confirmed that the L. maculans-susceptible response was due to the dominant negative nature of the abil-1 mutant. Highly induced camalexin levels made ABA mutants in Col-0 background (aba2-1, aba3-1, and abi4-1) appear resistant, but displayed enhanced susceptibility as double mutants with pad3-1, impaired in camalexin biosynthesis. beta-Aminobutyric acid (BABA) pretreatment of Ler-0 contributed to an elevated level of endogenous ABA after L. maculans inoculation. Comparisons between (RLM1co1)pad3 and rlmlLerpad3 showed that ABA and BABA enhancement of callose deposition requires induction from RLM1col. ABII, but not ABI2, was found to be involved in a feedback mechanism that modulates RLM1co, expression. Genetic analysis showed further that this feedback occurs upstream of ABI4 and that components downstream of ABI4 modulate ABIJ activity. ABA and BABA treatments of the L. maculans-susceptible callose synthase mutant pmr4 showed that ABA also induces a callose-independent resistance. Similar treatments enhanced callose depositions and induced resistance to L. maculans in oilseed rape, and BABA-induced resistance was found to be independent of salicylic acid.
Kaliff
Maria
M
Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, P.O. Box 7080, 750 07 Uppsala, Sweden. Maria.Kaliff@vbsg.slu.se
Staal
Jens
J
Myrenås
Mattias
M
Dixelius
Christina
C
D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D000613:Aminobutyrates / Q000494:pharmacology; D017360:Arabidopsis / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001203:Ascomycota; D029741:Brassica rapa / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D018506:Gene Expression Regulation, Plant; D005936:Glucans / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007211:Indoles / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry / Q000235:genetics / Q000382:microbiology; D015398:Signal Transduction; D013844:Thiazoles / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D000094162:Phytoalexins
D000040:Abscisic Acid; D000613:Aminobutyrates; D029681:Arabidopsis Proteins; D005936:Glucans; D006861:Hydrogen Peroxide; D007211:Indoles; D010749:Phosphoprotein Phosphatases; D013844:Thiazoles; D014157:Transcription Factors; C470421:ABI4 protein, Arabidopsis; C102405:camalexin; D000094162:Phytoalexins; C047667:3-aminobutyric acid; C048306:callose; C087434:ABI1 protein, Arabidopsis; C106443:ABI2 protein, Arabidopsis