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Hybrid production using lines with cytoplasmic male sterility (CMS) has become an important way to utilize heterosis in vegetables. Ogura CMS, with the advantages of complete pollen abortion, ease of transfer and a progeny sterility rate reaching 100%, is widely used in cruciferous crop breeding. The mapping, cloning, mechanism and application of Ogura CMS and fertility restorer genes in Brassica napus , Brassica rapa , Brassica oleracea and other cruciferous crops are reviewed herein, and the existing problems and future research directions in the application of Ogura CMS are discussed.

Petal color is an important agronomic trait in cabbage ( Brassica oleracea L. var. capitata ). Although the key gene BoCCD4 has been functionally characterized, the underlying molecular regulatory mechanism of petal color formation in cabbage is still unclear. In this study, we applied the transcriptome analysis of yellow petals from the cabbage inbred line YL-1 and white petals from the Chinese kale inbred line A192-1 and the BoCCD4 -overexpressing transgenic line YF-2 (YL-1 background), which revealed 1928 DEGs common to both the A192-1 vs. YL-1 and the YL-1 vs. YF-2 comparison groups. One key enzyme-encoding gene, BoAAO3 , and two key TF-encoding genes, Bo2g151880 (WRKY) and Bo3g024180 (SBP), related to carotenoid biosynthesis were significantly up-regulated in both the A192-1 and YF-2 petals, which was consistent with the expression pattern of BoCCD4 . We speculate that these key genes may interact with BoCCD4 to jointly regulate carotenoid biosynthesis in cabbage petals. This study provides new insights into the molecular regulatory mechanism underlying petal color formation in cabbage.

Cabbage ( Brassica oleracea L. var. capitata ) self-incompatibility is important for heterosis. However, the seed production of elite hybrid cannot be facilitated by honey bees due to the cross-incompatibility of the two parents. In this study, the self-compatibility of 58 winter cabbage inbred lines was identified by open-flower self-pollination (OS) and molecular techniques. Based on the NCBI database, a new class I S-haplotype-specific marker, PKC6F/PKC6R, was developed. Verification analyses revealed 9 different S-haplotypes in the 58 cabbage inbred lines; of these lines, 46 and 12 belonged to class I (S6, S7, S12, S14, S33, S45, S51, S68) and class II (S15) S-haplotypes, respectively. The coincidence rate between the self-compatibility index and S-haplotype was 91%. This study developed a Tri-Primer-PCR amplification method to rapidly select plants with specific S-haplotypes in biased segregated S-locus populations. Furthermore, it established an S-haplotype identification system based on these nine S-haplotypes. To overcome parental cross-incompatibility (18-503 and 18-512), an inbred line (18-2169) with the S15 haplotype was selected from the sister lines of self-incompatible 18-512 (S68, class I S-haplotype). The inbred line (18-2169) showed self-compatibility and cross-compatibility with 18-503. This study provides guidance for self-compatibility breeding in cabbage and predicts parental cross-incompatibility in elite combinations.

Key Message: A single nucleotide mutation of BoCER2 is the primary cause of the wax deficiency in cabbage. An effective allele-specific KASP marker was developed for marker-assisted selection of glossiness. TL28-1 is a novel spontaneous wax-deficient mutant with a glossy phenotype identified from cabbage. In this study, the genetic analysis suggested that the wax-deficient trait of TL28-1 was controlled by a single recessive gene. All wax monomers longer than 28 carbons were significantly decreased in TL28-1. Fine-mapping results showed that the wax-deficient locus wdtl28 was located at an 80-kb interval between BOL01-20 and BOL01-24 markers on chromosome 1. According to the genome annotation of B. oleracea, the ECERIFERUM2- LIKE (CER2-LIKE) gene, BoCER2, was identified as the candidate gene. Phylogenetic analysis showed that BoCER2 and other CER2-LIKEs from vascular plants formed a clade within the BAHD superfamily of acyltransferases. The BoCER2 transcript was detected in various tissues, including stem, leaf, flower, and silique, but not in the cabbage roots. Subcellular localization indicated that BoCER2 protein functions in the endoplasmic reticulum. Further sequence analysis showed that a single nucleotide mutation (G to A) is present in the BoCER2 coding sequence in TL28-1, leading to a stop codon (TGA), hence premature translation termination. Linkage analysis showed that the homozygotic mutational BoCER2 co-segregated with wax deficiency. Moreover, the complementation test suggested that BoCER2 from wild type can rescue the wax deficiency of TL28-1. These results indicate that BoCER2 mutation hinders the elongation of very-long-chain fatty acid precursors in TL28-1, leading to wax deficiency. The allele-specific KASP marker designed in this study could be effective for marker-assisted selection of glossiness., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: The aerial organs of most terrestrial plants are covered by cuticular waxes, which impart plants a glaucous appearance and play important roles in protecting against various biotic and abiotic stresses. Despite many glossy green (wax-defective) mutants being well characterized in model plants, little is known about the genetic basis of glossy green mutant in broccoli., Results: B156 is a spontaneous broccoli mutant showing a glossy green phenotype. Detection by scanning electron microscopy (SEM) and chromatography-mass spectrometry (GC-MS) revealed that B156 is a cuticular wax-defective mutant, lacking waxes mostly longer than C28. Inheritance analysis revealed that this trait was controlled by a single recessive gene, BoGL5. Whole-genome InDel markers were developed, and a segregating F 2 population was constructed to map BoGL5. Ultimately, BoGL5 was mapped to a 94.1 kb interval on C01. The BoCER2 gene, which is homologous to the Arabidopsis CER2 gene, was identified as a candidate of BoGL5 from the target interval. Sequence analyses revealed that Bocer2 in B156 harbored a G-to-T SNP mutation at the 485th nucleotide of the CDS, resulting in a W-to-L transition at the 162nd amino acid, a conserved site adjacent to an HXXXD motif of the deduced protein sequence. Expression analysis revealed that BoCER2 was significantly down-regulated in the leaves, stems, and siliques of B156 mutant than that of B3. Last, ectopic expression of BoCER2 in A. thaliana could, whereas Bocer2 could not, rescue the phenotype of cer2 mutant., Conclusions: Overall, this study mapped the locus determining glossy phenotype of B156 and proved BoCER2 is functional gene involved in cuticular wax biosynthesis which would promotes the utilization of BoCER2 to enhance plant resistance to biotic and abiotic stresses, and breeding of B. oleracea cultivars with glossy traits., (© 2021. The Author(s).)

Main Conclusion: From Brassica oleracea genome, 88 anthocyanin biosynthetic genes were identified. They expanded via whole-genome or tandem duplication and showed significant expression differentiation. Functional characterization revealed BoMYB113.1 as positive and BoMYBL2.1 as negative regulators responsible for anthocyanin accumulation. Brassica oleracea produces various health-promoting phytochemicals, including glucosinolates, carotenoids, and vitamins. Despite the anthocyanin biosynthetic pathways in the model plant Arabidopsis thaliana being well characterized, little is known about the genetic basis of anthocyanin biosynthesis in B. oleracea. In this study, we identified 88 B. oleracea anthocyanin biosynthetic genes (BoABGs) representing homologs of 46 Arabidopsis anthocyanin biosynthetic genes (AtABGs). Most anthocyanin biosynthetic genes, having expanded via whole-genome duplication and tandem duplication, retained more than one copy in B. oleracea. Expression analysis revealed diverse expression patterns of BoABGs in different tissues, and BoABG duplications showed significant expression differentiation. Additional expression analysis and functional characterization revealed that the positive regulator BoMYB113.1 and negative regulator BoMYBL2.1 may be key genes responsible for anthocyanin accumulation in red cabbage and ornamental kale by upregulating the expression of structural genes. This study paves the way for a better understanding of anthocyanin biosynthetic genes in B. oleracea and should promote breeding for anthocyanin content., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Leaf shape is an important agronomic trait in ornamental kale (Brassica oleracea L. var. acephala). Although some leaf shape-related genes have been reported in ornamental kale, the detailed mechanism underlying leaf shape formation is still unclear. Here, we report a lobed-leaf trait in ornamental kale, aiming to analyze its inheritance and identify the strong candidate gene., Results: Genetic analysis of F 2 and BC 1 populations demonstrate that the lobed-leaf trait in ornamental kale is controlled by a single dominant gene, termed BoLl-1 (Brassica oleracea lobed-leaf). By performing whole-genome resequencing and linkage analyses, the BoLl-1 gene was finely mapped to a 127-kb interval on chromosome C09 flanked by SNP markers SL4 and SL6, with genetic distances of 0.6 cM and 0.6 cM, respectively. Based on annotations of the genes within this interval, Bo9g181710, an orthologous gene of LATE MERISTEM IDENTITY 1 (LMI1) in Arabidopsis, was predicted as the candidate for BoLl-1, and was renamed BoLMI1a. The expression level of BoLMI1a in lobed-leaf parent 18Q2513 was significantly higher compared with unlobed-leaf parent 18Q2515. Sequence analysis of the parental alleles revealed no sequence variations in the coding sequence of BoLMI1a, whereas a 1737-bp deletion, a 92-bp insertion and an SNP were identified within the BoLMI1a promoter region of parent 18Q2513. Verification analyses with BoLMI1a-specific markers corresponding to the promoter variations revealed that the variations were present only in the lobed-leaf ornamental kale inbred lines., Conclusions: This study identified a lobed-leaf gene BoLMI1a, which was fine-mapped to a 127-kb fragment. Three variations were identified in the promoter region of BoLMI1a. The transcription level of BoLMI1a between the two parents exhibited great difference, providing new insight into the molecular mechanism underlying leaf shape formation in ornamental kale., (© 2021. The Author(s).)

Glucoraphanin is a major secondary metabolite found in Brassicaceae vegetables, especially broccoli, and its degradation product sulforaphane plays an essential role in anticancer. The fine mapping of sulforaphane metabolism quantitative trait loci (QTLs) in broccoli florets is necessary for future marker-assisted selection strategies. In this study, we utilized a doubled haploid population consisting of 176 lines derived from two inbred lines (86,101 and 90,196) with significant differences in sulforaphane content, coupled with extensive genotypic and phenotypic data from two independent environments. A linkage map consisting of 438 simple sequence repeats markers was constructed, covering a length of 1168.26 cM. A total of 18 QTLs for sulforaphane metabolism in broccoli florets were detected, 10 were detected in 2017, and the other 8 were detected in 2018. The LOD values of all QTLs ranged from 3.06 to 14.47, explaining 1.74-7.03% of the biochemical variation between two years. Finally, 6 QTLs (qSF-C3-1, qSF-C3-2, qSF-C3-3, qSF-C3-5, qSF-C3-6 and qSF-C7) were stably detected in more than one environment, each accounting for 4.54-7.03% of the phenotypic variation explained (PVE) and a total of 30.88-34.86% of PVE. Our study provides new insights into sulforaphane metabolism in broccoli florets and marker-assisted selection breeding in Brassica oleracea crops.

Main Conclusion: Comparative morphological, transcriptomic and phytohormone analyses reveal a defence network leading to PCD involved in cabbage hybrid lethality. Hybrid lethality (HL) plays an essential role in the stability of a population by blocking gene exchange between species, but the molecular mechanism remains largely undetermined. In this study, we performed phenotype, transcriptome and plant hormone analyses of HL in cabbage. Phenotype analysis confirmed that HL is characterised by a typical programmed cell death (PCD) process. A time-resolved RNA-Seq identified 2724 differentially expressed genes (DEGs), and functional annotations analyses revealed that HL was closely associated with the defence response. A defence regulation network was constructed based on the plant-pathogen interaction pathway and MAPK signalling pathway, which comprised DEGs related to Ca 2+ and hydrogen peroxide (H 2 O 2 ) leading to PCD. Moreover, important DEGs involved in hormone signal transduction pathways including salicylic acid (SA) and jasmonic acid (JA) were identified, which were further confirmed by endogenous and exogenous SA and JA measurements. Our results identified key genes and pathways in the regulating network of HL in cabbage, and might open the gate for revealing the molecular mechanism of HL in plants.

Main Conclusion: Chitinase family genes were involved in the response of Brassica oleracea to Fusarium wilt, powdery mildew, black spot and downy mildew. Abstract Chitinase, a category of pathogenesis-related proteins, is believed to play an important role in defending against external stress in plants. However, a comprehensive analysis of the chitin-binding gene family has not been reported to date in cabbage (Brassica oleracea L.), especially regarding the roles that chitinases play in response to various diseases. In this study, a total of 20 chitinase genes were identified using a genome-wide search method. Phylogenetic analysis was employed to classify these genes into two groups. The genes were distributed unevenly across six chromosomes in cabbage, and all of them contained few introns (≤ 2). The results of collinear analysis showed that the cabbage genome contained 1-5 copies of each chitinase gene (excluding Bol035470) identified in Arabidopsis. The heatmap of the chitinase gene family showed that these genes were expressed in various tissues and organs. Two genes (Bol023322 and Bol041024) were relatively highly expressed in all of the investigated tissues under normal conditions, exhibiting the expression characteristics of housekeeping genes. In addition, under four different stresses, namely, Fusarium wilt, powdery mildew, black spot and downy mildew, we detected 9, 5, 8 and 8 genes with different expression levels in different treatments, respectively. Our results may help to elucidate the roles played by chitinases in the responses of host plants to various diseases.

Cabbage (Brassica oleracea var. capitata L.) is widely cultivated in China and be of important economic value. In October 2019, all the plants of cabbage inbred line '2358' cultivated in greenhouses of the Chinese Academy of Agricultural Sciences (Beijing) were showing symptoms of leaf wilt. It usually took two weeks for the leaves to get completed wilted and the plants gradually died. It was approximately 550 plants affected, and 30 plants were collected and processed as samples. Symptomatic leaves were cut into small pieces (5×5 mm), surface sterilized with 75% ethanol for 30 s, and then sterilized with 8% NaClO for 3 mins, rinsed three times in sterile distilled water, plated on complete medium (CM: 3g Casein Enzymatic Hydrolysate + 3g Casein Acid Hydrolysate + 6g Yeast Extract+10g Sucrose + 15g Agar + 1L dH2O) and incubated at 27℃ for 6 days. Subsequently, the purified culture was obtained by tissue isolation and single-spored on CM. The colony on CM was up to about 50mm and 70mm in diameter after 4 and 7 days, respectively (Supplementary Fig. 2). At the same time, the edge of the colony gradually turned brown. Microscopic observation found that the diameter of the mycelium was about 5 µm (Supplementary Fig. 3). The conidia were transparent white and ovoid-shaped, about 0.3-0.5 µm in diameter (Supplementary Fig. 4). Fungus in liquid CM were spherical with surface hairs (Supplementary Fig. 1), which was consistent with the morphological characteristics of Chaetomium globosum. The rDNA internal transcribed spacer (ITS) of isolate ZM2019 was amplified using primers ITS1 (5'-TCCGTAGGTGAACCTGCGG-3') and ITS4 (5'- TCCTCCGCTTATTGATATGC-3') (Hong et al. 2013). The amplified product was sequenced and deposited in GenBank. The 573-bp amplicon (GenBank accession no. MN833403) showed a 100% homology to C. globosum isolate CES5 (MN173145). According to the morphological and molecular characterization, the fungus causing leaf blight on '2358' was identified as C. globosum. In order to further distinguish the pathogen species, the β-tubulin (tub2) gene region were amplified using primers T-F (5'-CCCCTGAACTACCCCACC-3') and T-R (5'-TATTTGACCCGACTGACC-3') and sequenced. Finally, we further identified this pathogen as C. globosum CBS 148.51 (Wang et al. 2016), according to the blast result of the sequence (GenBank accession no. MW252170) in National Center for Biotechnology Information (NCBI). To confirm the pathogenicity of this fungus, the leaves of 12 healthy seedlings of '2358' were inoculated by spraying 106 conidia/ml suspension and 12 seedlings inoculated with sterile water served as controls. All plants were incubated in a growth chamber maintained at 27℃. Ten days after inoculation, the leaves of all plants became wilted, which were consistent with the symptom in the natural state, while the control plants remained disease-free (Supplementary Fig. 6b and Fig. 6c). Subsequently, C. globosum was isolated from the inoculated seedlings again. The entire process from isolation to inoculation was repeated again and the same results were obtained. Re-isolation of C. globosum and inoculation of the host fulfiled Koch's postulates. C. globosum has been reported previously to occur on many horticulture plants such as Punica granatum (Guo et al. 2015) and Cannabis sativa (Chaffin et al. 2020); but no brassica species has been reported so far as susceptible to C. globosum. In this sense, this is the first report of leaf blight caused by C. globosum on cabbage in China, in greenhouse condition.

Key Message: Ogura CMS fertility-restored materials, with 18 chromosomes, normal seed setting, stable fertility and closer genetic background to the parent Chinese kale, were successfully developed in B. oleracea via a triploid strategy for the first time. Ogura cytoplasmic male sterility (CMS) is the most widely used sterile type in seed production for commercial hybrids of Brassica oleracea vegetables. However, the natural Ogura CMS restorer line has not been found in B. oleracea crops. In this study, the triploid strategy was used with the aim to create euploid B. oleracea progenies with the Rfo gene. The allotriploid AAC hybrid YL2 was used as a male parent to backcross with Ogura CMS Chinese kale. After successive backcrosses, the BC 2 Rfo-positive individual 16CMSF2-11 and its BC 3 progenies, with 18 chromosomes, were developed, which were morphologically identical to the parent Chinese kale. Compared with F 1 and BC 1 plants, it showed stable fertility performance, and regular meiosis behavior and could produce seeds normally under natural pollination. The genomic composition analysis of Rfo-positive progenies by using molecular markers showed that more than 87% of the C-genome components of BC 3 Rfo-progenies recovered to the parent Chinese kale, while most or all of the A n -genome segments were lost in 16CMSF2-11 and its progenies. The results suggested that the genetic background of Rfo-positive individuals was closer to that of the parent Chinese kale along with backcrossing. Hereof, the Ogura CMS fertility-restored materials of Chinese kale were successfully created via triploid strategy for the first time, providing a bridge for utilizing the Ogura CMS B. oleracea germplasm in the future. Moreover, our study indicates that the triploid strategy is effective for transferring genes from B. napus into B. oleracea.

Main Conclusion: CaLCuV-based VIGS effectively works in cabbage and contributes to efficient functional genomics research in Brassica crop species. Virus-induced gene silencing (VIGS), a posttranscriptional gene silencing method, is an effective technique for analysing the functions of genes in plants. However, no VIGS vectors have been available for Brassica oleracea until now. Here, tobacco rattle virus (TRV), pTYs and cabbage leaf curl virus (CaLCuV) gene-silencing vectors (PCVA/PCVB) were chosen to improve the VIGS system in cabbage using the phytoene desaturase (PDS) gene as an efficient visual indicator of VIGS. We successfully silenced the expression of PDS and observed photobleaching phenomena in cabbage in response to pTYs and CaLCuV, with the latter being more easy to operate and less expensive. The parameters potentially affecting the silencing efficiency of VIGS by CaLCuV in cabbage, including the targeting fragment strategy, inoculation method and incubation temperature, were then compared. The optimized CaLCuV-based VIGS system involves the following: an approximately 500 bp insert sequence, an Agrobacterium OD 600 of 1.0, use of the vacuum osmosis method applied at the bud stage, and an incubation temperature of 22 °C. Using these parameters, we achieved a stable silencing efficiency of 65%. To further test the effectiveness of the system, we selected the Mg-chelatase H subunit (ChlH) gene in cabbage and knocked down its expression, and we observed yellow leaves, as expected. We successfully applied the CaLCuV-based VIGS system to two other representative Brassica crop species, B. rapa and B. nigra, and thus expanded the application scope of this system. Our VIGS system described here will contribute to efficient functional genomics research in Brassica crop species.

Cabbage (Brassica oleracea var. capitata) is an important vegetable crop widely grown throughout the world, providing plentiful nutrients and health-promoting substances. To facilitate further genetics and genomic studies and crop improvement, we present here a high-quality reference genome for cabbage. We report a de novo genome assembly of the cabbage double-haploid line D134. A combined strategy of single-molecule real-time (SMRT) sequencing, 10× Genomics and chromosome conformation capture (Hi-C) produced a high quality cabbage draft genome. The chromosome-level D134 assembly is 529.92 Mb in size, 135 Mb longer than the current 02-12 reference genome, with scaffold N50 length being raised as high as 38 times. We annotated 44,701 high-quality protein-coding genes, and provided full-length transcripts for 45.59% of the total predicted gene models. Moreover, we identified novel genomic features like underrated TEs, as well as gene families and gene family expansions and contractions during B. oleracea evolution. The D134 draft genome is a cabbage reference genome assembled by SMRT long-read sequencing combined with the 10× Genomics and Hi-C technologies for scaffolding. This high-quality cabbage reference genome provides a valuable tool for improvement of Brassica crops.

Clubroot disease, a major plant root disease caused by Plasmodiophora brassicae , has become one of the most destructive diseases among cultivated cruciferous vegetables. However, clubroot-resistant Brassica oleracea materials are rare. A few clubroot-resistant cabbage varieties are available on the market, but all are Ogura cytoplasmic male sterile (CMS) types. Therefore, in this study, to reutilize the clubroot-resistant Ogura CMS germplasm of cabbage, a new fertility-restored Ogura CMS material, 16Q2-11, was used as a bridge to transfer the clubroot resistance (CR) gene from the Ogura CMS cytoplasm to the normal cytoplasm by a two-step method (a fertility restoration and cytoplasm replacement method). In the first cross for fertility restoration of Ogura CMS clubroot-resistant cabbage (FRCRC), 16Q2-11 was used as a restorer to cross with Ogura CMS materials containing the CR gene CRb2 . Eleven Rfo -positive progenies were generated, of which four contained CRb2 : F8-514, F8-620, F8-732 and F8-839. After inoculation with race 4 of P. brassicae , these four CRb2 -positive individuals showed resistance. Furthermore, F8-514 and F8-839 were then used as male parents in the second cross of FRCRC to cross with cabbage inbred lines, resulting in the successful introgression of the CRb2 gene into the inbred lines. All offspring produced from this step of cross, which had a normal cytoplasm, showed a high resistance to race 4 of P. brassicae and could be utilized for the breeding of clubroot-resistant cabbage varieties in the future. This is the first time that the Ogura CMS restorer has been used to restore the fertility of Ogura CMS clubroot-resistant cabbages, which could improve germplasm diversity in cabbage and provide a reference method for using CMS germplasm in Brassica crops., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© The Author(s) 2020.)

Ornamental kale is popular because of its colorful leaves and few studies have investigated the mechanism of color changes. In this study, an ornamental kale line (S2309) with three leaf colors was developed. Analysis of the anthocyanin, chlorophyll, and carotenoid contents and RNA-seq were performed on the three leaf color types. There was less chlorophyll in the white leaves and purple leaves than in the green leaves, and the anthocyanin content was greatest in the purple leaves. All the downregulated DEGs related to chlorophyll metabolism were detected only in the S2309_G vs. S2309_W comparison, which indicated that the decrease in chlorophyll content was caused mainly by the inhibition of chlorophyll biosynthesis during the leaf color change from green to white. Moreover, the expression of 19 DEGs involved in the anthocyanin biosynthesis pathway was upregulated. These results provide new insight into the mechanisms underlying the three-color formation., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The great majority of terrestrial plants produce epicuticular wax that is used to protect plants from a variety of biotic and abiotic stresses. Cabbage epicuticular wax is a white crystalline compound of various lipids. Wax-less cabbage has the characteristics of lustrous green leaves and beautiful exterior, which facilitates the brilliant green cabbage breeding. CGL-3 is a spontaneous wax-less mutant identified from cabbage. Genetic analysis indicated that the waxy deficiency of the mutant was controlled by a single dominant gene. To clarify the mechanism of the waxy deficiency, fine-mapping and transcriptome analysis of the wax-less gene, BoGL-3, were carried out in this study. The result of fine mapping showed that the wax-less gene, BoGL-3, was delimited in a 33.5-kb interval which is between the flanking marker C08-98 and the end of chromosome 8. Two cDNA libraries, constructed with wax-less cabbage CGL-3 and the wild-type cabbage WT, were sequenced for screening of the target gene BoGL-3. A total of 8340 genes were identified with significant differential expression between CGL-3 and WT. Among these genes, 3187 were up-regulated and 5153 were down-regulated in CGL-3. With homologous analysis, four differential expressed genes related to wax metabolism were obtained. Among these four genes, only Bol018504 is located within the region of fine-mapping. Bol08504 is homologous to CER1, which encodes fatty acid hydroxylase and plays an important role in wax synthesis in Arabidopsis. However, there was no difference of Bol08504 sequence between CGL-3 and WT. We suggested that Bol018504 was regulated by BoGL-3. The suppression of Bol018504 leads to the reduction of wax. These findings will be helpful to reveal the mechanism of the wax metabolism in cabbage and develop lustrous green cabbage germplasm material.

Gamma-tubulin gene is a very important house-keeping gene and plays key roles in cell division, microtubule nucleation and cell cycle regulation in both plants and animals. In this paper, we studied the gamma-tubulin gene silencing in Nicotiana tabacum var. Samsun NN using the recombinant PVX vector with D fragment of gamma-tubulin cDNA. Special phenotype appeared from recombinant PVX-vector-infected plants, the different morphological leaves grew alternatively in leaf layers (Figs.3-5), and all the buds fell off gradually (Fig.4), resulting in failure of all the microspores to develop to the tetrad stage (Fig.8). The silencing initiated from the apical tissue and kept on until it was mature (Figs.3, 4). There was the increasing of target gene mRNA obviously during gene silencing, even to exceed the positive control (Fig.6). The PVX vector was also suppressed strongly and could fluctuate to some degree (Fig.9), which was probably correlated with target gene mRNA expression.