Abstract
Ascorbate oxidase (AO) plays important roles in plant growth and development. Previously, we reported a cotton AO gene that acts as a positive factor in cell growth. Investigations on Gossypium hirsutum AO (GhAO) family genes and their multiple functions are limited. The present study identified eight GhAO family genes and performed bioinformatic analyses. Expression analyses of the tissue specificity and developmental feature of GhAOs displayed their diverse expression patterns. Interestingly, GhAO1A demonstrated the most rapid significant increase in expression after 1 h of light recovery from the dark. Additionally, the transgenic ao1-1/GhAO1A Arabidopsis lines overexpressing GhAO1A in the Arabidopsis ao1-1 late-flowering mutant displayed a recovery to the normal phenotype of wild-type plants. Moreover, compared to the ao1-1 mutant, the ao1-1/GhAO1A transgenic Arabidopsis presented delayed leaf senescence that was induced by the dark, indicating increased sensitivity to hydrogen peroxide (H2O2) under normal conditions that might be caused by a reduction in ascorbic acid (AsA) and ascorbic acid/dehydroascorbate (AsA/DHA) ratio. The results suggested that GhAOs are functionally diverse in plant development and play a critical role in light responsiveness. Our study serves as a foundation for understanding the AO gene family in cotton and elucidating the regulatory mechanism of GhAO1A in delaying dark-induced leaf senescence.
Highlights
Ascorbate oxidase (AO; EC 1.10.3.3), is an enzyme that exists only in plants and fungi [1] and participates in numerous physiological processes, including plant growth and development, responses to environmental stress, and regulation of cellular reduction/oxidation homeostasis
To identify the AO gene family members in G. hirsutum, the reported AO protein sequences from A. thaliana, O. sativa, G. max, Z. mays, and S. bicolor were used as direct queries to perform a blastp search against the G. hirsutum protein databases, which identified a total of eight AO genes
We identified eight AO gene family members in G. hirsutum through a genome-wide investigation and characterized their phylogenetic relationship, evolution and synteny, exon-intron structure, and conserved motif distribution
Summary
Ascorbate oxidase (AO; EC 1.10.3.3), is an enzyme that exists only in plants and fungi [1] and participates in numerous physiological processes, including plant growth and development, responses to environmental stress, and regulation of cellular reduction/oxidation (redox) homeostasis. As a glycoprotein of the blue copper oxidase enzyme family [2,3], AO contains three distinct copper domains [4,5,6,7] that endow the function of oxidizing ascorbic acid (AsA) to monodehydroascorbate (MDHA) and of synchronously catalyzing molecular oxygen reduction to water [6,8]. The expression of AO is regulated by complex transcriptional and post-transcriptional controls [9], including induced and reduced expression at the mRNA level by hormones [10,11] and abiotic stresses [11,12,13], respectively. Previous studies have shown that AO may be involved in light responsiveness, with cis-elements for light regulation in a known AO promoter region, and the suppression or overexpression of AO causes late flowering or delayed dark-induced senescence in vitro [2,10,12,22]
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