Genome-Wide Identification of the F-box Gene Family and Expression Analysis under Drought and Salt Stress in Barley

The F-box protein-encoding gene family plays an essential role in plant stress resistance.In present study,126 non-redundant F-box genes were identified in barley(Hordeum vulgare L.,Hv).The corresponding proteins contained 165–887 amino acid residues and all were amphiphilic,except 5 proteins.Phylogenetic analysis of F-box protein sequences in barley and stress-related F-box protein sequences in wheat and Arabidopsis thaliana(At)was used to classify barley F-box genes are divided into 9 subfamilies(A–I).A structure-based sequence alignment demonstrated that F-box proteins were highly conserved with a total of 10 conserved motifs.In total,124 F-box genes were unevenly distributed on 7 chromosomes;another 2 genes have not been anchored yet.The gene structure analysis revealed high variability in the number of exons and introns in F-box genes.Comprehensive analysis of expression profiles and phylogenetic tree analysis,a total of 12 F-box genes that may be related to stress tolerance in barley were screened.Of the 12 detected F-box genes,8 and 10 were upregulated after drought and salt stress treatments,respectively,using quantitative real-time polymerase chain reaction(qRT-PCR).This study is the first systematic analysis conducted on the F-box gene family in barley,which is of great importance for clarifying this family’s bioinformatic characteristics and elucidating its function in barley stress resistance.These results will serve as a theoretical reference for subsequent research on molecular regulation mechanisms,genetic breeding,and improvement.

Phylogenetic Analysis on SLG and SRK Genes in Brassica and Raphanus

S-locus genes were cloned from three Brassica napus and three B. campestris lines by using PCR walking and homologuesequence methods. A phylogenetic gene tree was constructed based on the six cloned genes and fifty-one previouslyreported SLG/SRK genes of Brassica and Raphanus. The SLGs from R. sativus were dispersed in the phylogenetic treeintermingling with SLG/SRKs from B. oleracea, B. napus and B. campestris. The SLG/SRK genes of classⅡclusteredindependently in one group. The SLG/SRK genes of classⅠshowed to be more divergent than classⅡgenes. Theseresults suggested that the divergence of classⅠand classⅡ should have occurred before the differentiation of thegenera Brassica and Raphanus. In addition, SLG and SRK of the same S haplotypes belonged to the same class. Itsuggested that class-Ⅰ and class-Ⅱ group divergence occurred first, and then SLG and SRK diverged. The three SC SRKgenes from B. napus and B. campestris were grouped into one cluster, displaying difference from the SC SLG of B.oleracea. These three SC SRK genes were close to SI SRK of SI1300, SI271 and guanyou in phylogenetic relationships.These results indicated that SC and SI genes diverged more recently. It is not clear yet whether the differentiation of SCand SI genes was earlier than the differentiation of Brassica and Raphanus. Studies based on more genes are necessaryfor a comprehensive elucidation of the phylogenetic relationships in Brassicaceae.

Recent advances in identification of male specificity determinant and its function in S-RNase-mediated gametophytic self-incompatibility

S-RNase-mediated gametophytic self-incompatibility （GSI） is controlled by a multiallelic S-locus at which two separate genes, the female （pistil） and male （pollen） specificity determinants, are tightly linked. This review described both the identification of pollen specific F-box genes, SLF/SFBs, in Antirrhinum, Petunia and Prunus species and the demonstration of SLF/SFB as pollen determinant together with their functions in GSI response. Recent studies of how the pollen determinant functions in pollination reaction revealed that pollen determinant interacted with S-RNases in a non-allele-specific manner. It targeted all of the non-self S-RNases for ubiquitination through a functional SCF complex and subsequent degradation via 26S proteasome pathway in compatible reaction. It allows pollen tube to reach into the embryo sac and to finish double fertilization. In incompatible response, the intact self S-RNases were left to function as a cytotoxin that degrades self-pollen tube RNA, resulting in the cessation of pollen tube growth.

配子体型自交不亲和调控机制的研究进展

植物自交不亲和是一种广泛存在的生殖隔离机制,可有效防止自交促进杂交,维持基因型多样性.配子体型自交不亲和是植物界分布最为广泛的自交不亲和类型,是以S-RNase的细胞毒性为基础的分子调控过程.归纳总结了配子体自交不亲和中雌雄蕊S因子的研究进展,并在此基础上对配子体型自交不亲和研究领域的难点和方向进行了分析和展望,以期促进对配子体型自交不亲和调控机制的深入研究.

Arabidopsis F-box gene FOA1 involved in ABA signaling

The expression of FOAl （F-box overexpressed/oppressed ABA signaling） in different organs of Arabidopsis, and in response to ABA and NaCI, was analyzed. The expression level of FOAl is higher in the root and is lower in the stem, and is induced rapidly by ABA and NaC1. The phenotypes of T-DNA insertion mutant foal and FOAl overexpression lines FOAloxl and FOAlox2 were analyzed. The foal mutant exhibited a lower germination rate, shorter root length, more stomatal opening, in- creased proline accumulation and hypersensitivity to ABA compared with the wild type. In contrast, the overexpression lines showed lower sensitivity to ABA than the wild type. The expression levels of several ABA and stress-responsive transcription factors and genes were altered in the foal mutant in response to ABA. Compared with the wild type, the expression levels of ABA-responsive transcription factors were higher, but ABA and stress-responsive genes were lower in foal mutant. This study demonstrates that FOAl is an ABA signaling-related gene, and may play a negative role in ABA signaling.

Rice miR394 suppresses leaf inclination through targeting an F-box gene, LEAF INCLINATION 4

Rice leaf inclination is an important agronomic trait, closely related to plant architecture and yield.Identification of genes controlling leaf inclination would assist in crop improvement. Although various factors,including the plant hormones auxin and brassinosteroids,have been shown to regulate lamina joint development,the role of microRNAs in regulating leaf inclination remains largely unknown. Here, we functionally characterize the role of rice miR394 and its target, LEAF INCLINCATION 4(LC4), which encodes an F-box protein, in the regulation of leaf inclination. We show that miR394 and LC4 work,antagonistically, to regulate leaf lamina joint development and rice architecture, by modulating expansion and elongation of adaxial parenchyma cells. Suppressed expression of miR394, or enhanced expression of LC4,results in enlarged leaf angles, whereas reducing LC4 expression by CRISPR/Cas9 leads to reduced leaf inclination, suggesting LC4 as candidate for use in rice architecture improvement. LC4 interacts with SKP1, a component of the SCF E3 ubiquitin ligase complex, and transcription of both miR394 and LC4 are regulated by auxin. Rice plants with altered expression of miR394 or LC4 have altered auxin responses, indicating that the miR394-LC4 module mediates auxin effects important for determining rice leaf inclination and architecture.

A Systematic Phenotypic Screen of F-box Genes Through a Tissue-specific RNAi-based Approach in Drosophila

F-box proteins are components of the SCF （SkpA-Cullin 1-F-box） E3 ligase complexes, acting as the specificity-determinants in targeting substrate proteins for ubiquitination and degradation. In humans, at least 22 out of 75 F-box proteins have experimentally documented substrates, whereas in Drosophila 12 F-box proteins have been characterized with known substrates. To systematically investigate the genetic and molecular functions of F-box proteins in Drosophila, we performed a survey of the literature and databases. We identified 45 Drosophila genes that encode proteins containing at least one F-box domain. We collected publically available RNAi lines against these genes and used them in a tissue-specific RNAi-based phenotypic screen. Here, we present our systematic phenotypic dataset from the eye, the wing and the notum. This dataset is the first of its kind and represents a useful resource for future studies of the molecular and genetic functions of F-box genes in Drosophila. Our results show that, as expected, F-box genes in Drosophila have regulatory roles in a diverse array of processes including cell proliferation, cell growth, signal transduction, and cellular and animal survival.

F-box gene FOA2 regulates GA-and ABA-mediated seed germination in Arabidopsis

Dear Editor, GA and ABA antagonize each other in controlling seed germination, but the molecular mechanism is not fully understood. The F-box proteins act as the most important SCF （SKP1, cullin/CDC53, F-box protein） complex subunit of the ubiquitin （Ub）- 26S proteasome system, mediate diverse physiological processes ranging from hormonal signaling cascades to environmental stress responses （Santner and Estelle, 2010）. We previously demonstrated that FOAl （F-box overexpressed/oppressed ABA signaling） is an ABA signaling-related gene,

A Truncated F-Box Protein Confers the Dwarfism in Cucumber

Dwarfism is an important plant architecture trait in crop breeding（Peng et al.,1999;Sasaki el al.,2002）.In cucurbits.the compact plant type was proposed to develop new varieties for the once-over mechanical harvest for concentrated fruit set and higher densities（Li et al.,2011;Mondal et al.,2011）.

A Rice Panicle Mutant Created by Transformation with an Antisense cDNA Library

A rice （Oryza sativa L.） mutant displaying defects in panicle development was identified among transformants in a transgenic mutagenlzed experiment using an antlsense cDNA library prepared from young rice panicles. In the mutant, the average splkelet number was reduced to 59.8 compared with 104.3 in wild-type plants. In addition, the seed-setting rate of the mutant was low （39.3%） owing to abnormal female development. Genetic analysis of T1 and T2 progeny showed that the traits segregated In a 3 （mutant） ： 1 （wild type） ratio and the mutation was cosegregated with the transgene. Southern blot and thermal asymmetric interlaced polymerase chain reaction analyses showed that the mutant had a single T-DNA insertion on chromosome 5, where no gene was tagged. Sequencing analysis found that the transgenic antisense cDNA was derived from a gene encoding an F-box protein in chromosome 7 with unidentified function. This and another four homologous genes encoding putative F-box proteins form a gene cluster. These results indicate that the phenotyplc mutations were most likely due to the silencing effect of the expressed transgenic antisense construct on the member（s） of the F-box gene cluster.