Two New Alleles of the abscisic aldehyde oxidase 3 Gene Reveal Its Role in Abscisic Acid Biosynthesis in Seeds

Abstract

The abscisic aldehyde oxidase 3 (AAO3) gene product of Arabidopsis catalyzes the final step in abscisic acid (ABA) biosynthesis. An aao3-1 mutant in a Landsberg erecta genetic background exhibited a wilty phenotype in rosette leaves, whereas seed dormancy was not affected (Seo et al., 2000a). Therefore, it was speculated that a different aldehyde oxidase would be the major contributor to ABA biosynthesis in seeds (Seo et al., 2000a). Through a screening based on germination under high-salt concentration, we isolated two mutants in a Columbia genetic background, initially named sre2-1 and sre2-2 (for salt resistant). Complementation tests with different ABA-deficient mutants indicated that sre2-1 and sre2-2 mutants were allelic to aao3-1, and therefore they were renamed as aao3-2 and aao3-3, respectively. Indeed, molecular characterization of the aao3-2 mutant revealed a T-DNA insertional mutation that abolished the transcription of AAO3 gene, while sequence analysis of AAO3 in aao3-3 mutant revealed a deletion of three nucleotides and several missense mutations. Physiological characterization of aao3-2 and aao3-3 mutants revealed a wilty phenotype and osmotolerance in germination assays. In contrast to aao3-1, both aao3-2 and aao3-3 mutants showed a reduced dormancy. Accordingly, ABA levels were reduced in dry seeds and rosette leaves of both aao3-2 and aao3-3. Taken together, these results indicate that AAO3 gene product plays a major role in seed ABA biosynthesis.

Enhancement of Abscisic Acid Sensitivity and Reduction of Water Consumption in Arabidopsis by Combined Inactivation of the Protein Phosphatases Type 2C ABI1 and HAB1

“…The double mutants were also more sensitive than single parental mutants to inhibition of germination and early growth mediated by osmotic stress. Imposing osmotic stress at the seedling stage leads to increased ABA biosynthesis and consequently to early growth arrest (Lopez-Molina et al, 2001;Gonzalez-Guzman et al, 2004). Thus, whereas in adult plants ABA plays a crucial role to coordinate the various aspects of the low water potential response to allow plant survival, in seeds and seedlings ABA action is mainly focused to prevent germination and to arrest seedling growth.…”

ABA-deficiency and molecular mechanisms involved in the dehydration response and ripening of citrus fruit

“…The hormone ABA has been involved in postharvest quality and stress tolerance of fruit (Serrano et al, 2004;Alférez et al, 2005;Cantín et al, 2007).…”

“…Physiological characterization of the Arabidopsis aao3 mutant showed an ABA-deficient phenotype, osmotolerance in germination and wilty leaves (Seo et al, 2004;González-Guzman et al, 2004;Barrero et al, 2006). In addition, Seo et al (2004) demonstrated that these mutants (AAO1-AAO4) displayed reduced or not affected dormancy because a partial redundancy among genes.…”

“…Focusing on ABA, natural and induced knockout mutants of biosynthetic genes have been characterized (Armstrong et al, 1995;Schwartz et al, 1997;Xiong et al, 2001;Seo et al, 2004;González-Guzman et al, 2004;Barrero et al, 2006;North et al, 2007;Fan et al, 2009;Frey et al, 2012).…”

Ruta de transducción de señal del ácido abscísico: Regulación por HAB1 y dianas de interacción. La inactivación combinada de PP2Cs como herramienta biotecnológica para incrementar la tolerancia a sequía en plantas

“…Este fenotipo leve en las semillas se ha atribuido a la redundancia de genes postulándose que otros genes de AAOs podrían estar implicados en la biosíntesis de ABA [222]. Aunque la identificación de alelos nulos aao3 que exhiben fenotipos deficientes en ABA importantes en semillas indican que probablemente AAO3 es único gen de las AAOs que participa en la síntesis de ABA [66,221].…”