Abstract
GAox is a key enzyme for the transformation of gibberellins, and belongs to the 2-ketoglutarate dependent dioxygenase gene family (2ODD). However, a systematic analysis of GAox in the angiosperm L. chinense has not yet been reported. Here, we identified all LcGAox gene family members in L. chinense, which were classified into the three subgroups of GA20ox, C19GA2ox, and C20GA2ox. Comparison of the gene structure, conserve motifs, phylogenetic relationships, and syntenic relationships of gibberellin oxidase gene families in different species indicated that the gene functional differences may be due to the partial deletion of their domains during evolution. Furthermore, evidence for purifying selection was detected between orthologous GAox genes in rice, grape, Arabidopsis, and L. chinense. Analysis of the codon usage patterns showed that mutation pressure and natural selection might have induced codon usage bias in angiosperms; however, the LcGAox genes in mosses, lycophytes, and ambarella plants exhibited no obvious codon usage preference. These results suggested that the gibberellin oxidase genes were more primitive. The gene expression pattern was analyzed in different organs subjected to multiple abiotic stresses, including GA, abscisic acid (ABA), and chlormequat (CCC) treatment, by RNA-seq and qRT-PCR, and the stress- and phytohormone-responsive cis-elements were counted. The results showed that the synthesis and decomposition of GA were regulated by different LcGAox genes in the vegetative and reproductive organs of L. chinense, and only LcGA2ox1,4, and 7 responded to the NaCl, polyethylene glycol, 4 °C, GA, ABA, and CCC treatment in the roots, stems, and leaves of seedlings at different time periods, revealing the potential role of LcGAox in stress resistance.
Highlights
As a class of tetracyclic diterpenes, gibberellins (GA) are indispensable for the growth and development of plants
We found that the G-Box and ABRE motifs were ubiquitous and relatively abundant in all the gibberellin oxidases of L. chinense, and in comparison, with other LcGAox genes, the number was higher in the promoters of LcGA20ox2, LcGA20ox5, LcGA2ox1-4, and LcGA2ox7 (Figure 8a)
We identified 13 gibberellin oxidase genes based on publicly-available
Summary
As a class of tetracyclic diterpenes, gibberellins (GA) are indispensable for the growth and development of plants. The GA synthesis pathway can be divided into three main steps: the first step is the catalysis of geranylgeranyl pyrophosphat (GGPP). From ent-kaurene by the enzymes of CPS and KS in the piroplasmid; the second step is the synthesis of GA12 according to KO and KAO enzymes by the products of the previous step in the endomembrane; and the third step is the synthesis of physiologically active GA under the catalysis of the gibberellin oxidase (GAox) enzyme [9,10,11]. Due to their excellent material properties and ornamental value, they are widely planted in China and the United States for landscaping and wood production [12]. GAox belongs to the 2OG-Fe (II) oxygenase superfamily, which is divided into multiple small families based on structural and functional differences [11]
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