Identification,Structure Analyses and Expression Pattern of the ERF Transcription Factor Family in Coffea arabica

Members of the ERF Family of Transcription Factors play an important role in plant development and gene expression that regulates responses to biotic and abiotic stress.This work identified 36 ERF family genes in Coffea arabica within the AP2/ERF full domain,using the EST-based genomic resource of the Brazilian Coffee Genome Project.The ERF family genes were classified into nine of the ten existing groups through phylogenetic analysis of the deduced amino acid sequences and comparison with the sequences of the ERF family genes in Arabidopsis.In addition to the AP2 domain,other conserved domains were identified,typical of members of each group.The in silico analysis and expression profiling showed high levels of expression for libraries derived from tissues of fruits,leaves and flowers as well as for libraries subjected to water stress.These results suggest the participation of the ERF family genes of C.arabica in distinct biological functions,such as control of development,maturation,and responses to water stress.The results of this work imply in the selection of promising genes for further functional characterizations that will provide a better understanding of the complex regulatory networks related to plant development and responses to stress,opening up opportunities for coffee breeding programs.

紫花苜蓿转录因子基因MsAP_(2)的克隆及转化

紫花苜蓿(Medicago sativa)为重要的豆科牧草植物,研究紫花苜蓿转录因子基因MsAP_(2)的功能,为探究MsAP_(2)的信号转导网络提供理论指导和材料基础,也为紫花苜蓿生物技术育种提供一定的参考和借鉴。运用RT-PCR技术克隆MsAP_(2),利用DNA重组技术构建3302-3flag-AP_(2)植物表达载体,并利用农杆菌介导法对紫花苜蓿进行遗传转化,对再生植株进行转基因鉴定、基因表达量分析、内源激素的测定(脱落酸、细胞分裂素、生长素和赤霉素)和表型鉴定。结果表明,成功获得转MsAP_(2)紫花苜蓿植株,与野生型相比,转基因植株的MsAP_(2)表达量和激素水平均发生明显改变,转基因植株呈现早衰性状,叶片形态和大小发生改变,根系生长受到抑制,分枝数发生改变。

Cloning and Expression Analysis of an AP2/ERF Gene and Its Responses to Phytohormones and Abiotic Stresses in Rice

Ethylene response factors （ERFs） play important roles in response to plant biotic and abiotic stresses. In this study, a gene encoding a putative AP2/ERF domain-containing protein was isolated by screening a SSH cDNA library from rice and designated as Oryza sativa AP2/ERF-like protein （OsAP2LP） gene. OsAP2LP is 1491 bp in length, interrupted by seven introns, and encodes a putative protein of 348 amino acids. Temporal and spatial expression analysis showed that the OsAP2LP gene was preferentially expressed in roots, panicles, mature embryos and seeds in rice. Real-time quantitative PCR analysis indicated that the expression levels of the OsAP2LP gene were increased under the treatments of drought and gibberellin but decreased under the treatments of low temperature, salt, abscisic acid （ABA） and zeatin. Taken together, these results suggest that OsAP2LP might be involved in stress responses, and probably plays roles as a transcription regulator when plants response to cold, salt and drought stresses through ABA and gibberellin pathways.

The Jasmonate-Responsive AP2/ERF Transcription Factors AaERF1 and AaERF2 Positively Regulate Artemisinin Biosynthesis in Artemisia annua L.

Plants of Artemisia annua produce artemisinin, a sesquiterpene lactone widely used in malaria treatment. Amorpha-4,11-diene synthase （ADS）, a sesquiterpene synthase, and CYP71AV1, a P450 monooxygenase, are two key enzymes of the artemisinin biosynthesis pathway. Accumulation of artemisinin can be induced by the phytohormone jasmonate （JA）. Here, we report the characterization of two JA-responsive AP2 family transcription factors-AaERF1 and AaERF2-from A. annua L. Both genes were highly expressed in inflorescences and strongly induced by JA. Yeast one- hybrid and electrophoretic mobility shift assay （EMSA） showed that they were able to bind to the CRTDREHVCBF2 （CBF2） and RAVlAAT （RAA） motifs present in both ADS and CYP71AV1 promoters. Transient expression of either AaERF1 or AaERF2 in tobacco induced the promoter activities of ADS or CYP71AV1, and the transgenic A. annua plants overexpressing either transcription factor showed elevated transcript levels of both ADS and CYP71AV1, resulting in increased accumulation of artemisinin and artemisinic acid. By contrast, the contents of these two metabolites were reduced in the RNAi transgenic lines in which expression of AaERF1 or AaERF2 was suppressed. These results demonstrate that AaERF1 and AaERF2 are two positive regulators of artemisinin biosynthesis and are of great value in genetic engineering of arte- misinin production.

Hairy Leaf 6, an AP2/ERF Transcription Factor, Interacts with OsWOX3B and Regulates Trichome Formation in Rice

Trichome formation has been extensively studied as a mechanistic model for epidermal cell differentiation and cell morphogenesis in plants. However, the genetic and molecular mechanisms underlying trichome formation （i.e., initiation and elongation） in rice remain largely unclear. Here, we report an AP2/ERF transcription factor, Hairy Leaf 6 （HL6）, which controls trichome formation in rice. Functional analyses revealed that HL6 transcriptionally regulates trichome elongation in rice, which is dependent on functional OsWOX3B, a homeodomain-containing protein that acts as a key regulator in trichome initiation. Biochemical and molecular genetic analyses demonstrated that HL6 physically interacts with OsWOX3B, and both of them regulate the expression of some auxin-related genes during trichome formation, in which OsWOX3B likely enhances the binding ability of HL6 with one of its direct target gene, OsYUCCA5. Popu- lation genetic analysis indicated that HL6 was under negative selection during rice domestication. Taken together, our findings provide new insights into the molecular regulatory network of trichome formation in rice.

Genome-wide identification and analysis of AP2/ERF transcription factors related to camptothecin biosynthesis in Camptotheca acuminata

Camptotheca acuminata produces camptothecin(CPT),a monoterpene indole alkaloid(MIA)that is widely used in the treatment of lung,colorectal,cervical,and ovarian cancers.Its biosynthesis pathway has attracted significant attention,but the regulation of CPT biosynthesis by the APETALA2/ethylene-responsive factor(AP2/ERF)transcription factors(TFs)remains unclear.In this study,a systematic analysis of the AP2/ERF TFs family in C.acuminata was performed,including phylogeny,gene structure,conserved motifs,and gene expression profiles in different tissues and organs(immature bark,cotyledons,young flower,immature fruit,mature fruit,mature leaf,roots,upper stem,and lower stem)of C.acuminata.A total of 198 AP2/ERF genes were identified and divided into five relatively conserved subfamilies,including AP2(26 genes),DREB(61 genes),ERF(92 genes),RAV(18 genes),and Soloist(one gene).The combination of gene expression patterns in different C.acuminata tissues and organs,the phylogenetic tree,the co-expression analysis with biosynthetic genes,and the analysis of promoter sequences of key enzymes genes involved in CPT biosynthesis pathways revealed that eight AP2/ERF TFs in C.acuminata might be involved in CPT synthesis regulation,which exhibit relatively high expression levels in the upper stem or immature bark.Among these,four genes(Cac AP2/ERF123,Cac AP2/ERF125,Cac AP2/ERF126,and Cac AP2/ERF127)belong to the ERF–B2 subgroup;two genes(Cac AP2/ERF149 and Cac AP2/ERF152)belong to the ERF–B3 subgroup;and two more genes(Cac AP2/ERF095 and Cac AP2/ERF096)belong to the DREB–A6 subgroup.These results provide a foundation for future functional characterization of the AP2/ERF genes to enhance the biosynthesis of CPT compounds of C.acuminata.

A seed-specific AP2-domain transcription factor from soybean plays a certain role in regulation of seed ger-mination

Plant seed development and germination are under strict temporal and spatial regulation, and tran-scription factors play important roles in this regulation. In the present study we identified an EST ex-pressed specifically in the developing soybean seeds. The full length of the gene was obtained through further RACE analysis and the gene was named GmSGR. Sequence analysis revealed that this gene belonged to the AP2/ERF transcription factor family. Its AP2 domain had the highest similarity with that of the A-3 member AtABI4 of DREB subgroup in the AP2/ERF family in Arabidopsis. GmSGR did not exhibit transcriptional activation activity in the yeast assay system. GmSGR was overexpressed in Arabidopsis and the germination rates of the transgenic seeds were significantly higher than that of the wild type seeds under higher concentrations of ABA and glucose respectively. However, the germina-tion rates of the transgenic seeds were lower than that of control under salt stress. The expression of AtEm6 and AtRD29B was higher in the seedlings of the transgenic plants than that in the wild-type seedlings. These results suggest that GmSGR may confer reduced ABA sensitivity and enhanced salt sensitivity to the transgenic seeds through regulating the expression of AtEm6 and AtRD29B genes.