外源BoCAL基因对花椰菜花球形态发生的调节及其遗传

花椰菜和结球甘蓝是芸薹属甘蓝种的两个变种,前者的BoCAL基因发生提前终止突变而失去了原有的功能,而后者的BoCAL基因具有完整的编码区。在农杆菌的介导下,我们获得了BoCAL转基因花椰菜。T2代的遗传研究表明,外源BoCAL基因转入后花椰菜转基因植株都没有形成花球,而是只形成松散的由花蕾组成的绿色花序。这一结果说明,花椰菜BobCAL被甘蓝BoCAL互补了,转基因花椰菜因此失去了形成花球的能力。这些转基因植株自交到T3代时花序的形态特征与T2代一致,为松散的绿色花序,但是花序出现的时间与T1代相比提早了15天。将转基因花椰菜与野生型花椰菜杂交,结果发现杂交后代的植株形成夹杂有花蕾的花球,且花序出现的时间大大推迟,在播种后135天后才形成花球。     

外源BoCAL基因对花椰菜花球形态发生的调节及其遗传

花椰菜和结球甘蓝是芸薹属甘蓝种的两个变种,前者的BobCAL基因发生提前终止突变而失去了原有的功能,而后者的BoCAL基因具有完整的编码区。在农杆菌的介导下,我们获得了BoCAL转基因花椰菜。T_2代的遗传研究表明,外源BoCAL基因转入后花椰菜转基因植株都没有形成花球,而是只形成松散的由花蕾组成的绿色花序。这一结果说明,花椰菜BobCAL被甘蓝BoCAL互补了,转基因花椰菜因此失去了形成花球的能力。这些转基因植株自交到T_3代时花序的形态特征与T_2代一致,为松散的绿色花序,但是花序出现的时间与T_1代相比提早了15天。将转基因花椰菜与野生型花椰菜杂交,结果发现杂交后代的植株形成夹杂有花蕾的花球,且花序出现的时间大大推迟,在播种后135天后才形成花球。     

Mutations in the Arabidopsis SWC6 gene, encoding a component of the SWR1 chromatin remodelling complex, accelerate flowering time and alter leaf and flower development

Mutations affecting the Arabidopsis SWC6 gene encoding a putativeorthologue of a component of the SWR1 chromatin remodellingcomplex in plants have been characterized. swc6 mutations causeearly flowering, shortened inflorescence internodes, and alteredleaf and flower development. These phenotypic defects resemblethose of the photoperiod independent early flowering 1 (pie1)and early in short days 1 (esd1) mutants, also affected in homologuesof the SWR1 complex subunits. SWC6 is a ubiquitously expressednuclear HIT-Zn finger-containing protein, with the highest levelsfound in pollen. Double mutant analyses suggest that swc6 abolishesthe FLC-mediated late-flowering phenotype of plants carryingactive alleles of FRI and of mutants of the autonomous pathway.It was found that SWC6 is required for the expression of theFLC repressor to levels that inhibit flowering. However, theeffect of swc6 in an flc null background and the down-regulationof other FLC-like/MAF genes in swc6 mutants suggest that floweringinhibition mediated by SWC6 occurs through both FLC- and FLC-likegene-dependent pathways. Both genetic and physical interactionsbetween SWC6 and ESD1 have been demonstrated, suggesting thatboth proteins act in the same complex. Using chromatin immunoprecipitation,it has been determined that SWC6, as previously shown for ESD1,is required for both histone H3 acetylation and H3K4 trimethylationof the FLC chromatin. Altogether, these results suggest thatSWC6 and ESD1 are part of an Arabidopsis SWR1 chromatin remodellingcomplex involved in the regulation of diverse aspects of plantdevelopment, including floral repression through the activationof FLC and FLC-like genes. Key words: Arabidopsis, chromatin remodelling, floral repression, HIT-Zn finger, phase transition, SWR1 complex     

Floral homeotic gene expression defines developmental arrest stages inBrassica oleracea L. vars.botrytis anditalica

Brassica oleracea L. vars.italica (broccoli) andbotrytis (cauliflower) both undergo developmental arrests which result in heading phenotypes. We characterized these arrested tissues at the morphological and molecular levels, and defined the developmental changes that ensue after arrest has been broken. We found that the order of floral organ initiation and the positions of resulting floral organ primordia in this species differed in some respects from that ofArabidopsis, which is a member of the same family, Brassicaceae. We also cloned homologs of theArabidopsis floral homeotic genesAPETALA1 (AP1) andAPETALA3 (AP3) fromB. oleracea and characterized their expression patterns. We found that theAP1 homolog was expressed in some of the meristems of arrest-stage cauliflower, providing evidence that this tissue is florally determined. In broccoli, both the API andAP3 homologs were expressed. However, the spatial pattern of expression of the broccoliAP1 homolog differed from that ofArabidopsis. In addition, we identified a homolog of theCAULIFLOWER (CAL) gene,BoiCAL, from broccoli. The predicted amino acid sequence indicated that theBoiCAL gene product does not contain the mutation thought to be responsible for the early arrest exhibited in cauliflower (Kempin et al. 1995), but contains other changes that might play a role in the broccoli heading phenotype.The GenBank accession numbers for the sequences reported here are: U67451 (Boi2AP1); U67452 (Boi2AP1); U67453 (Boi1AP3); U67455 (Boi2AP3); U67456 (BobAP3); and U67454 (BoiCAL)     

The distribution of BoCAL-a alleles in Brassica oleracea is consistent with a genetic model for curd development and domestication of the cauliflower

The characteristic curd of cauliflower (Brassica oleracea var. botrytis L.) consists of proliferating, arrested inflorescence and floral meristems. However, the origins and events leading to the domestication of this important crop trait remain unclear. A similar phenotype observed in the ap1-1/cal-1 mutant of Arabidopsis thaliana led to speculation that the orthologous genes from B. oleracea may be responsible for this characteristic trait. We have carried out a detailed molecular and genetic study, which allows us to present a genetic model based on segregation of recessive alleles at specific, mapped loci of the candidate genes BoCAL and BoAP1. This accounts for differences in stage of arrest between cauliflower and Calabrese broccoli (B. oleracea var. italica Plenck), and predicts the intermediate stages of arrest similar to those observed in Sicilian Purple types. Association of alleles of BoCAL-a with curding phenotypes of B. oleracea is also demonstrated through a survey of crop accessions. Strong correlations exist between specific alleles of BoCAL-a and discrete inflorescence morphologies. These complementary lines of evidence suggest that the cauliflower curd arose in southern Italy from a heading Calabrese broccoli via an intermediate Sicilian crop type. PCR-based assays for the two key loci contributing to curd development are suitable for adoption in marker-assisted selection.     

Transformation of rice with the Arabidopsis floral regulator LEAFY causes early heading

Onset of flowering, or heading date, is an important agronomic trait of cereal crops such as rice and early-heading varieties are required for certain regions in which rice is cultivated. Since the floral control gene LEAFY from Arabidopsis can dramatically accelerate flowering in dictoyledonous plants, the usefulness of LEAFY for manipulating heading date in rice has been tested. Constitutive expression of LEAFY from the cauliflower mosaic virus 35S promoter caused early flowering in transgenic rice, with a heading date that was 26–34 days earlier than that of wild-type plants. Early flowering was accompanied by a small yield penalty and some panicle abnormality. These observations suggest that floral regulatory genes from Arabidopsis are useful tools for heading date improvement in cereal crops.     

Apple has two orthologues of FLORICAULA/LEAFY involved in flowering

Two orthologues of FLORICAULA/LEAFY, AFL1 and AFL2 (apple FLO/LFY), were isolated from the floral buds of apple trees. Their expression was detected in various tissues and during differentiation of the floral buds. Furthermore, the flowering effectiveness of each gene was assessed with transgenic Arabidopsis. Both AFL1 and AFL2 showed high homology to each other (90%) and a high degree of similarity to PTLF and PEAFLO (70%), which are homologues of FLO/LFY from poplar and pea, respectively. RNA blot analysis showed that AFL1 was expressed only in the floral bud during the transition from vegetative to reproductive growth, whereas AFL2 was expressed in vegetative shoot apex, floral buds, floral organs and root. Genomic Southern analysis showed that apple had other homologues in addition to AFL1 and AFL2. The transgenic Arabidopsis with over-expressed AFL2 showed accelerated flowering and gave rise to several solitary flowers from rosette axils directly. AFL1 had similar effects, but the phenotypes of the transgenic Arabidopsis with AFL1 were weaker than those with AFL2. These results suggest that both genes are involved in flower differentiation in apple.     

芸苔属植物CAL基因的结构特征与花球的形态遗传

Cauliflower curd is composed structurally of a number of shortened shoots on which there are tremendous amount of naked apical meristems. The authors isolated four pure lines of different curd types from cauliflower (Brassica oleracea L. var. botrytis) accessions: smooth curd (curd-s), haired curd (curd-h), crystal curd (curd-c) and thorned curd (curd-t). BobCAL genes was cloned separately from each pure line by PCR amplification and a termination mutation from AAG to TAG was found in the fifth exon of all four sequences, whereas DNA sequences of 638 bp upstream of the stop codons were identical, demonstrating that BobCAL is not the sole regulator of flower buds and cauline on curd. After crosses of cauliflower with cabbage (B.oleracea var. capitata) or broccoli (B.oleracea var. italica), the resultant F1 plants failed to form curd and had the diversity of inflorescence which implicates the relatedness of CAL to other regulators. One homologous gene of CAL, BcpCAL was isolated from Chinese cabbage (B.campestris L. ssp. pekinensis) and it was found not to have the termination mutation in the fifth exon, and thus the structure of BcpCAL gene was analyzed. The results offer molecular and genetic evidence for the study of biological function of CAL and morphological genetics of curd.     

Benzylaminopurine induces phenocopies of floral meristem and organ identity mutants in wild-typeArabidopsis plants

Arabidopsis thaliana (L.) Heynh. has been used as a model system to investigate the regulatory genes that control and coordinate the determination, differentiation and morphogenesis of the floral meristem and floral organs. We show here that benzylaminopurine (BAP), a cytokinin, influences flower development inArabidopsis and induces partial phenocopies of known floral homeotic mutants. Application of BAP to wild-type inflorescences at three developmental stages results in: (i) increase in floral organ number; (ii) formation of abnormal floral organs and (iii) induction of secondary floral buds in the axils of sepals. These abnormalities resemble the phenotypes of mutants,clv1 (increase in organ number),ap1,ap2,ap3 (abnormal floral organs) andap1 (secondary floral buds in the axils of first-whorl organs). In addition, BAP induces secondary floral buds in the axils of perianth members ofapt2-6, ap3-1 andag mutants, and accentuates the phenotype of theapt2-1 mutant to resemble theapt2-6 mutant. These observations suggest that exogenous BAP suppresses the normal functioning of the genes for floral meristem identity and thereby affects flower development and the later stages of floral organ differentiation.Abbreviations BAP N6-benzylaminopurine - CK cytokinin     

Effect of incident radiation integral on cauliflower growth and development after curd initiation

Two field experiments were conducted to assess the response of cauliflower cv. “Nautilus F1” to different radiation integrals after curd initiation by covering the plants with different levels (0, 38, 50 and 68%) of neutral shading materials during the autumn 1998 and summer 2000. Cauliflower growth and development declined with increasing shade levels after curd initiation. Total above ground dry matter increased linearly with accumulated incident radiation integral after curd initiation, however, under lower radiation conditions, the rate of increase per unit incident radiation integral was greater than under higher radiation conditions. Moreover, radiation conversion coefficient declined linearly with increasing incident radiation integrals up to approximately 6.1 MJ m⁻² d⁻¹ and thereafter, declined more slowly with further increase in incident radiation integrals. Therefore, dry matter accumulation was potentially more efficient under lower incident radiation than higher incident radiation levels. Radiation conversion coefficients for plants under low incident radiation levels were greater than under high incident radiation levels. Curd growth also increased linearly with increasing accumulated incident radiation integral with greater mean relative curd dry matter increase per MJ under lower incident radiation conditions than higher incident radiation levels.     

EMF Genes Interact with Late-Flowering Genes to Regulate Arabidopsis Shoot Development

To investigate the genetic mechanisms regulating the transitionfrom vegetative to reproductive phase in Arabidopsis, doublemutants between two embryonic flower (emf) and 12 differentlate-flowering mutants were constructed and analyzed. Doublemutants in all combinations displayed the emf phenotypes withoutforming rosettes during early development; however, clear variationsbetween different double mutants were observed during late development,fwa significantly enhanced the vegetative property of both emfmutants by producing a high number of sessile leaves withoutany further reproductive growth in emf1 fwa double mutants.It also produced numerous leaf-like flower structures similarto those in leafy ap1 double mutant in emf1 fwa double mutants.Nine late-flowering mutants, ft, fca, ld, fd, fpa, fe, fy, fha,and fve, caused different degrees of increase in the numberof sessile leaves, the size of inflorescence, and the numberof flowers only in weak emf1 and emf2 mutant alleles background.Two late-flowering mutants, co and gi, however, had no effecton either emf1 and emf2 mutant alleles in double mutants. Ourresults suggest that FWA function in distinct pathways fromboth EMF genes to regulate flower competence by activating geneswhich specify floral meristem identity. CO and GI negativelyregulate both EMF genes, whereas the other nine late-floweringgenes may interact with EMF genes directly or indirectly toregulate shoot maturation in Arabidopsis. ¹ To whom correspondence should be addressed.     

The FLOWERING LOCUS T/TERMINAL FLOWER 1 family in Lombardy poplar

Genes in the FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1)family have been shown to be important in the control of theswitch between vegetative and reproductive growth in severalplant species. We isolated nine members of the FT/TFL1 familyfrom Lombardy poplar (Populus nigra var. italica Koehne). Sequenceanalysis of the members of the FT/TFL1 family revealed considerablehomology within their coding regions both among family membersand to the members of the same family in Arabidopsis, tomatoand grapevine. Moreover, members of this family in all fourspecies examined display a common exon–intron organization.Phylogenetic analysis revealed that the genes fall into fourdifferent clades: two into the TFL1 clade; five into the FTclade; and one each into the MOTHER OF FT AND TFL1 and BROTHEROF FT AND TFL1 clades. One gene in the TFL1 clade, PnTFL1, isexpressed in vegetative meristems, and transgenic Arabidopsisthat ectopically expressed PnTFL1 had a late-flowering phenotype.The expression patterns of two genes in the FT clade, PnFT1and PnFT2, suggested a role for them in the promotion of flowering,and transgenic Arabidopsis that ectopically expressed eitherPnFT1 or PnFT2 had an early-flowering phenotype.     

A spectrum of genes expressed during early stages of rice panicle and flower development

To unravel gene expression patterns during rice inflorescence development, particularly at early stages of panicle and floral organ specification, we have characterized random cloned cDNAs from developmental-stage-specific libraries. cDNA libraries were constructed from rice panicles at the stage of branching and flower primordia specification or from panicles undergoing floral organogenesis. Partial sequence analysis and expression patterns of some of these random cDNA clones from these two rice panicle libraries are presented. Sequence comparisons with known DNA sequences in databases reveal that approximately sixtyeight per cent of these expressed rice genes show varying degrees of similarity to genes in other species with assigned functions. In contrast, thirtytwo per cent represent uncharacterized genes. cDNAs reported here code for potential rice homologues of housekeeping molecules, regulators of gene expression, and signal transduction molecules. They comprise both single-copy and multicopy genes, and genes expressed differentially, both spatially and temporally, during rice plant development. New rice cDNAs requiring specific mention are those with similarity toCOP1, a regulator of photomorphogenesis inArabidopsis; sequence-specific DNA binding plant proteins like AP2-domain-containing factors; genes that specify positional information in shoot meristems like leucine-rich-repeat-containing receptor kinases; regulators of chromatin structure like Polycomb domain protein; and also proteins induced by abiotic stresses.     

A Serine/Threonine Protein Kinase Gene Isolated by an in vivo Binding Procedure Using the Arabidopsis Floral Homeotic Gene Product, AGAMOUS

During the course of characterizing fragments bound to an Arabidopsisfloral homeotic protein AGAMOUS in vivo, a gene encoding a putativeserine/threonine protein kinase was found on one of the fragments.The deduced 426 amino acid residues of the gene, named APK2a,are 65% identical to a previously reported Arabidopsisserine/threonineprotein kinase, APKla. The gene is composed of 6 exons and mapsat 10 cM from the upper end of chromosome 1. Northern hybridizationexperiments indicated that the gene is strongly expressed inleaves, moderately in roots, and very weakly in flowers. Furtherin situ analysis of the expression in floral buds showed thatthe APK2a gene is expressed at pedicels, is not expressed atthe floral organ primordia of wild type floral buds, but ismoderately expressed in the floral organ primordia of the agamousmutant. In vitro binding assay suggests that the AGAMOUS proteinbinds to a sequence similar to, but different from, the knownMADS-binding consensus sequences, the CArG box, located 3' downstreamof the APK2a gene. These results suggest that APK2a gene expressionis negatively regulated by the AG protein. A close homologue of the APK2a gene, named APK2b, was also isolatedfrom the Arabidopsis cDNA library. The expression pattern ofthe APK2b gene differs from that of APK2a. It is strongly expressedin leaves, moderately in flowers, and weakly in roots. ⁴Present address: Biomolecular Engineering Research Institute,6-2-3, Fruedai, Suita, Osaka, 565 Japan.     

MORPHOLOGY OF THE CURD OF CAULIFLOWER

Sadik , Sidki . (U. California, Davis.) Morphology of the curd of cauliflower. Amer. Jour. Bot. 49(3): 290–297. Illus. 1962.—The development of the curd and inflorescence of cauliflower, Brassica oleracea Linn., var. botrytis D.C., is described. The cultivars ‘Snowball M’ and ‘February-Early-March’ were studied. The curd has a nonfasciated and monopodial type of branching. Curd initiation of ‘Snowball M’ is not dependent on vernalization, but the curd of ‘February-Early-March’ and the floral primordia of both cultivars are initiated only after vernalization. Associated with flowering is the disruption of the curd by the elongation of some of the inflorescence branches. The initiation of leaves, branches, and floral primordia follows a 5 + 8 phyllotaxy throughout all stages of development. This system of phyllotaxy changes at the time of initiation of floral parts.