Because plants have a sessile lifestyle, they must adjust to numerous external stimuli and coordinate their growth and development accordingly. The plant hormones, a group of structurally unrelated small molecules, are central to the integration of diverse environmental cues with a plant’s genetic program. The ‘classical’ phytohormones, identified during the first half of the twentieth century, are auxin, abscisic acid, cytokinin, gibberellin and ethylene. More recently, several additional compounds have been recognized as hormones, including brassinosteroids, jasmonate, salicylic acid, nitric oxide and strigolactones. Plants also use several peptide hormones to regulate various growth responses, but this class of hormones is beyond our scope here. With the application of genetic approaches, mainly in Arabidopsis thaliana, many aspects of hormone biology have been elucidated. Most hormones are involved in many different processes throughout plant growth and development. This complexity is reflected by the contributions of hormone synthesis, transport and signaling pathways, as well as by the diversity of interactions among hormones to control growth responses.

Genetic screens resulted in the identification of many of the proteins involved in hormone signaling and the analysis of these proteins has contributed significantly to our current models of hormone action. One particularly exciting outcome is the recent identification of receptors for auxin, gibberellin, jasmonate and abscisic acid. Though far from complete, our improved understanding of hormone perception and signaling has allowed for comparisons between hormones. From these it is clear that some hormones (cytokinins, ethylene and the brassinosteroids) use well-characterized signaling mechanisms. On the other hand, the identification and characterization of the auxin and jasmonate receptors, as well as proteins in gibberellin signaling, have highlighted a novel mechanism for hormone perception in which the ubiquitin–proteasome pathway has a central role. [from: Santner A., Mark E., Recent advances and emerging trends in plant hormone signalling (2009) Nature 459: 1071-1078]

Abscisic acid (ABA), a type of plant hormone, is thought to be involved in the induction of dormancy, stomatal closure, and physiological functions such as flower falling and leaf falling. The biosynthesis of this substance is carried out by oxidation of abscisin aldehyde, and it is suggested that a specific aldehyde oxidase (AO) catalyzes the reaction. The CosmoBio Antibody Collection (CAC) has prepared three antibodies for detecting AO gene products cloned from Arabidopsis thaliana, and an antibody for detection of corn ascorbic acid peroxidase (APT).

In higher plants aldehyde oxidases (AO) appear to be homo- and heterodimeric assemblies of AO subunits with probably different physiological functions. AO-delta seems to be involved in the last step of abscisic acid biosynthesis, at least in leaves and seeds. In vitro, AO-delta oxidizes abscisic aldehyde to abscisic acid (ABA). In vitro, AO-delta also uses indole-3-aldehyde (IAld), benzaldehyde, 1-naphthaldehyde and cinnamaldehyde as substrate; the AAO2-AAO3 dimer also uses abscisic aldehyde as substrate.

Source: Professor Koichi Koshiba, Tokyo Metropolitan University Graduate School of Science and Technology Department of Life Science

References:
Seo, M., Koiwai, H., Akaba, S., Komano, T., Oritani, T., Kamiya, Y. and Koshiba, T. (2000) Abscisic aldehyde oxidase in leaves of Arabidopsis thaliana. Plant J. 23:481-488.

Because plants have a sessile lifestyle, they must adjust to numerous external stimuli and coordinate their growth and development accordingly. The plant hormones, a group of structurally unrelated small molecules, are central to the integration of diverse environmental cues with a plant’s genetic program. The ‘classical’ phytohormones, identified during the first half of the twentieth century, are auxin, abscisic acid, cytokinin, gibberellin and ethylene. More recently, several additional compounds have been recognized as hormones, including brassinosteroids, jasmonate, salicylic acid, nitric oxide and strigolactones. Plants also use several peptide hormones to regulate various growth responses, but this class of hormones is beyond our scope here. With the application of genetic approaches, mainly in Arabidopsis thaliana, many aspects of hormone biology have been elucidated. Most hormones are involved in many different processes throughout plant growth and development. This complexity is reflected by the contributions of hormone synthesis, transport and signaling pathways, as well as by the diversity of interactions among hormones to control growth responses.

Genetic screens resulted in the identification of many of the proteins involved in hormone signaling and the analysis of these proteins has contributed significantly to our current models of hormone action. One particularly exciting outcome is the recent identification of receptors for auxin, gibberellin, jasmonate and abscisic acid. Though far from complete, our improved understanding of hormone perception and signaling has allowed for comparisons between hormones. From these it is clear that some hormones (cytokinins, ethylene and the brassinosteroids) use well-characterized signaling mechanisms. On the other hand, the identification and characterization of the auxin and jasmonate receptors, as well as proteins in gibberellin signaling, have highlighted a novel mechanism for hormone perception in which the ubiquitin–proteasome pathway has a central role. [from: Santner A., Mark E., Recent advances and emerging trends in plant hormone signalling (2009) Nature 459: 1071-1078]

Abscisic acid (ABA), a type of plant hormone, is thought to be involved in the induction of dormancy, stomatal closure, and physiological functions such as flower falling and leaf falling. The biosynthesis of this substance is carried out by oxidation of abscisin aldehyde, and it is suggested that a specific aldehyde oxidase (AO) catalyzes the reaction. The CosmoBio Antibody Collection (CAC) has prepared three antibodies for detecting AO gene products cloned from Arabidopsis thaliana, and an antibody for detection of corn ascorbic acid peroxidase (APT).

In higher plants aldehyde oxidases (AO) appear to be homo- and heterodimeric assemblies of AO subunits with probably different physiological functions. AO-delta seems to be involved in the last step of abscisic acid biosynthesis, at least in leaves and seeds. In vitro, AO-delta oxidizes abscisic aldehyde to abscisic acid (ABA). In vitro, AO-delta also uses indole-3-aldehyde (IAld), benzaldehyde, 1-naphthaldehyde and cinnamaldehyde as substrate; the AAO2-AAO3 dimer also uses abscisic aldehyde as substrate.

Source: Professor Koichi Koshiba, Tokyo Metropolitan University Graduate School of Science and Technology Department of Life Science

References:
Seo, M., Koiwai, H., Akaba, S., Komano, T., Oritani, T., Kamiya, Y. and Koshiba, T. (2000) Abscisic aldehyde oxidase in leaves of Arabidopsis thaliana. Plant J. 23:481-488.