GATA transcription factors are transcriptional regulatory proteins that contain a characteristic type-IV zinc finger DNA-binding domain and recognize the conserved GATA motif in the promoter sequence of target genes. Previous studies demonstrated that plant GATA factors possess critical functions in developmental control and responses to the environment. To date, the GATA factors in soybean (Glycine max) have yet to be characterized. Thus, this study identified 64 putative GATA factors from the entire soybean genomic sequence. The chromosomal distributions, gene structures, duplication patterns, phylogenetic tree, tissue expression patterns, and response to low nitrogen stress of the 64 GATA factors in soybean were analyzed to further investigate the functions of these factors. Results indicated that segmental duplication predominantly contributed to the expansion of the GATA factor gene family in soybean. These GATA proteins were phylogenetically clustered into four distinct subfamilies, wherein their gene structure and motif compositions were considerably conserved. A comparative phylogenetic analysis of the GATA factor zinc finger domain sequences in soybean, Arabidopsis (Arabidopsis thaliana), and rice (Oryza sativa) revealed four major classes. The GATA factors in soybean exhibited expression diversity among different tissues; some of these factors showed tissue-specific expression patterns. Numerous GATA factors displayed upregulation or downregulation in soybean leaf in response to low nitrogen stress, and two GATA factors GATA44 and GATA58 were likely to be involved in the regulation of nitrogen metabolism in soybean. Overexpression of GmGATA44 complemented the reduced chlorophyll phenotype of the Arabidopsis ortholog AtGATA21 mutant, implying that GmGATA44 played an important role in modulating chlorophyll biosynthesis. Overall, our study provides useful information for the further analysis of the biological functions of GATA factors in soybean and other crops.

Chlorophyll plays an essential role in photosynthetic light harvesting and energy transduction in green tissues of higher plants and is closely related to photosynthesis and crop yield. Identification of transcription factors (TFs) involved in regulating chlorophyll biosynthesis is still limited in soybean (Glycine max), and the previously identified GmGATA58 is suggested to potentially modulate chlorophyll and nitrogen metabolisms, but its complete function is still unknown. In this study, subcellular localization assay showed that GmGATA58 was localized in the nucleus. Histochemical GUS assay and qPCR assay indicated that GmGATA58 was mainly expressed in leaves and responded to nitrogen, light and phytohormone treatments. Overexpression of GmGATA58 in the Arabidopsis thaliana ortholog AtGATA21 (gnc) mutant complemented the greening defect, while overexpression in Arabidopsis wild-type led to increasing chlorophyll content in leaves through up-regulating the expression levels of the large of chlorophyll biosynthetic pathway genes, but suppressing plant growth and yield, although the net photosynthetic rate was slightly improved. Dual-luciferase reporter assay also supported that GmGATA58 activated the transcription activities of three promoters of key chlorophyll biosynthetic genes of soybean in transformed protoplast of Arabidopsis. It is concluded that GmGATA58 played an important role in regulating chlorophyll biosynthesis, but suppressed plant growth and yield in transgenic Arabidopsis.

Polygalacturonase (PG) is an essential hydrolytic enzyme responsible for pectin degradation and thus plays an important role in fruit softening and other cell separation processes. PG protein is encoded by a multigene family, however, the members of PG gene family in kiwifruit (Actinidia chinensis) have not been extensively identified. In this study, a total of 51 AcPG genes in kiwifruit genome were identified. They are phylogenetically clustered into seven clades, and of them AcPG4 and AcPG18 with other known PG genes involved in fruit softening from peach, pear, papaya and melon form a small cluster together. The members of kiwifruit PG gene family consist of three to nine exons and two to eight introns, and their exon/intron structures are generally conserved in all clades except the clade D and E. During fruit softening of kiwifruit ‘Donghong’ under ambient temperature, cell wall modifying enzymes, including PG, PL (pectate and pectin lyases), and PE (pectinesterase, also known as pectin methylesterase, PME) showed a different activity profile, and of them, PG and PE activities largely correlated with the change of pectin content and firmness. Moreover, only 11 AcPG genes were highly or moderately expressed in softening fruit, and of which three AcPG genes (AcPG4, AcPG18, and AcPG8, especially the former two) has been found to strongly correlate with the profile of PG activity and pectin content, as well as fruit firmness, suggesting that they maybe play an important role in fruit softening. Thus, our findings not only benefit the functional characterization of kiwifruit PG genes, but also provide a subset of potential PG candidate genes for further genetic manipulation.

Herba epimedii (Epimedium), a traditional Chinese medicine, has been widely used as a kidney tonic and antirheumatic medicine for thousands of years. In Epimedium, flavonoids have been demonstrated to be the main bioactive components (BCs). However, the molecular biosynthetic and regulatory mechanisms of flavonoid-derived BCs remain obscure. In this study, we isolated twelve structural genes and two putative transcription factors (TFs) in the flavonoid pathway. Phytochemical analysis showed that the total content of four representative BCs (epimedin A, B, C and icariin) decreased slightly or dramatically in two lines of E. sagittatum during leaf development. Transcriptional analysis revealed that two R2R3-MYB TFs (EsMYBA1 and EsMYBF1), together with a bHLH TF (EsGL3) and WD40 protein (EsTTG1), were supposed to coordinately regulate the anthocyanin and flavonol-derived BCs biosynthesis in leaves. Overexpression of EsFLS (flavonol synthase) in tobacco resulted in increased flavonols content and decreased anthocyanins content in flowers. Moreover, EsMYB12 negatively correlated with the accumulation of the four BCs, and might act as a transcriptional repressor in the flavonoid pathway. Therefore, the anthocyanin pathway may coordinate with the flavonol-derived BCs pathway in Epimedium leaves. A better understanding of the flavonoid biosynthetic and regulatory mechanisms in E. sagittatum will facilitate functional characterization, metabolic engineering and molecular breeding studies of Epimedium species.

Epimedium sagittatum (Sieb. et Zucc.) Maxim, a popular traditional Chinese medicinal plant, has been widely used for treating sexual dysfunction and osteoporosis in China. The main bioactive components in herba epimedii are prenylated flavonol glycosides, which are end products of a branch of the flavonoid biosynthetic pathway. The MYB transcription factors (TF) act as activators or repressors to regulate the flavonoid pathway. In this study, 13 full-length cDNA clones of R2R3-MYB TFs from E. sagittatum (designated as EsMYB1 to EsMYB13) were isolated and characterized. Sequence similarity and phylogenetic analysis placed nine R2R3-MYB members of epimedii into five subgroups of the Arabidopsis R2R3-MYB family, while four members were not clustered into a defined subgroup. The number and length of introns from epimedii R2R3-MYB genes varied significantly, but intron positions and phases were well conserved. Expression patterns of epimedii R2R3-MYB genes in various tissues showed diverse. Finally, it is suggested that five epimedii R2R3-MYB genes may be involved in regulating the flavonoid pathway and could be used as valuable candidate genes for metabolic engineering studies in future. Sequence information of 13 R2R3-MYB genes discovered here will also provide an entry point into the overview of whole R2R3-MYB family in epimedii.