Overexpression of an F-box protein gene disrupts cotyledon vein patterning in Arabidopsis

Identification, Classification and Characterization Analysis of FBXL Gene in Cotton

F-box/LR (FBXL), Leucine-rich repeats in F-box proteins, belongs to the Skp1-Cullin1-F-box protein (SCF) E3 ligase family. FBXL genes play important roles in plant growth, such as plant hormones, responses to environmental stress, and floral organ development. Here, a total of 518 FBXL genes were identified and analyzed in six plant species. Phylogenetic analysis showed that AtFBXLs, VvFBXLs, and GrFBXLs were clustered into three subfamilies (Ⅰ-Ⅲ). Based on the composition of the F-box domain and carboxyl-terminal amino acid sequence, FBXL proteins were classified into three types (Type-A/-B/-C). Whole-genome duplication (WGD) along with tandem duplications and segmental contributed to the expansion of this gene family. The result indicates that four cotton species are also divided into three subfamilies. FBXLs in cotton were classified into three clades by phylogenetic and structural analyses. Furthermore, expression analyses indicated that the expression patterns of GhFBXLs in different cotton tissues were different. The highly expressed of GH_A07G2363 in 5-8 mm anthers, indicates that this gene might play a role in the reproductive process, providing candidate genes for future studies on cotton fertility materials. This study provides an original functional opinion and a useful interpretation of the FBXL protein family in cotton.

F-Box Genes in the Wheat Genome and Expression Profiling in Wheat at Different Developmental Stages

Genes of the F-box family play specific roles in protein degradation by post-translational modification in several biological processes, including flowering, the regulation of circadian rhythms, photomorphogenesis, seed development, leaf senescence, and hormone signaling. F-box genes have not been previously investigated on a genome-wide scale; however, the establishment of the wheat (Triticum aestivum L.) reference genome sequence enabled a genome-based examination of the F-box genes to be conducted in the present study. In total, 1796 F-box genes were detected in the wheat genome and classified into various subgroups based on their functional C-terminal domain. The F-box genes were distributed among 21 chromosomes and most showed high sequence homology with F-box genes located on the homoeologous chromosomes because of allohexaploidy in the wheat genome. Additionally, a synteny analysis of wheat F-box genes was conducted in rice and Brachypodium distachyon. Transcriptome analysis during various wheat developmental stages and expression analysis by quantitative real-time PCR revealed that some F-box genes were specifically expressed in the vegetative and/or seed developmental stages. A genome-based examination and classification of F-box genes provide an opportunity to elucidate the biological functions of F-box genes in wheat.

Diverse and dynamic roles of F-box proteins in plant biology

The SCF complex is a widely studied multi-subunit ring E3 ubiquitin ligase that tags targeted proteins with ubiquitin for protein degradation by the ubiquitin 26S-proteasome system (UPS). The UPS is an important system that generally keeps cellular events tightly regulated by purging misfolded or damaged proteins and selectively degrading important regulatory proteins. The specificity of this post-translational regulation is controlled by F-box proteins (FBPs) via selective recognition of a protein-protein interaction motif at the C-terminal domain. Hence, FBPs are pivotal proteins in determining the plant response in multiple scenarios. It is not surprising that the FBP family is one of the largest protein families in the plant kingdom. In this review, the roles of FBPs, specifically in plants, are compiled to provide insights into their involvement in secondary metabolites, plant stresses, phytohormone signalling, plant developmental processes and miRNA biogenesis.