Leaf-like sepals induced by ectopic expression of a SHORT VEGETATIVE PHASE (SVP)-like MADS-box gene from the basal eudicot Epimedium sagittatum

Epimedium L. (Berberidaceae, Ranales), a perennial traditional Chinese medicinal herb, has become a new popular landscape plant for ground cover and pot culture in many countries based on its excellent ornamental characteristics and, distinctive and diverse floral morphology. However, little is known about the molecular genetics of flower development in Epimedium sagittatum. Here, we describe the characterization of EsSVP that encodes a protein sharing 68%, 54% and 35% similarity with SVP, AGAMOUS-like 24 (AGL24) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) in Arabidopsis, respectively. Quantitative RT-PCR (qRT-PCR) indicated that EsSVP transcripts were principally found in petiole and leaf tissues, with little expression in roots and flowers and no in fruits. The highest EsSVP expression was observed in leaves. The flowering time of 35S::EsSVP in most Arabidopsis thaliana and in all petunia plants was not affected in both photoperiod conditions, but 35S::EsSVP 5# and 35S::EsSVP 1# Arabidopsis lines induced late and early flowering under long day (LD, 14 hr light/10 hr dark) and short day (SD, 10 hr light/14 hr dark) conditions, respectively. The 35S::EsSVP Arabidopsis produced extra secondary inflorescence or floral meristems in the axils of the leaf-like sepals with excrescent trichomes, and leaf-like sepals not able to enclose the inner three whorls completely. Moreover, almost all transgenic Arabidopsis plants showed persistent sepals around the completely matured fruits. Upon ectopic expression of 35S::EsSVP in Petunia W115, sepals were enlarged, sometimes to the size of leaves; corollas were greenish and did not fully open. These results suggest that EsSVP is involved in inflorescence meristem identity and flowering time regulation in some conditions. Although the SVP homologs might have suffered functional diversification among diverse species between core and basal eudicots, the protein functions are conserved between Arabidopsis/Petunia and Epimedium

Isolated Thellungiella shoots do not require roots to survive NaCl and Na2SO4 salt stresses

Shoots of Thellungiella derived by micropropagation were used to estimate the plants' salt tolerance and ability to regulate Na+ uptake. Two species with differing salt tolerances were studied: Thellungiella salsuginea (halophilla), which is less tolerant, and Thellungiella botschantzevii, which is more tolerant. Although the shoots of neither ecotype survived at 700 mM NaCl or 200 mM Na2SO4, micropropagated shoots of T. botschantzevii were more tolerant to Na2SO4 (10–100 mM) and NaCl (100–300 mM). In the absence of roots, Na2SO4 salinity reduced shoot growth more dramatically than NaCl salinity. Plantlets of both species were able to adapt to salt stress even when they did not form roots. First, there was no significant correlation between Na+ accumulation in shoots and Na+ concentration in the growth media. Second, K+ concentrations in the shoots exposed to different salt concentrations were maintained at equivalent levels to control plants grown in medium without NaCl or Na2SO4. These results suggest that isolated shoots of Thellungiella possess their own mechanisms for enabling salt tolerance, which contribute to salt tolerance in intact plants

Cloning and structural analysis of the anthocyanin pigmentation locus Rt of Petunia hybrida: characterization of insertion sequences in two mutant alleles

Anthocyanin biosynthesis in flowers of Petunia hybrida is controlled by the regulatory genes an1, an2 and an11. Seven classes of cDNA clones homologous to transcripts that are down-regulated in an1−, an2− and an11− mutants were isolated via differential cDNA cloning. Genetic mapping, antisense RNA experiments and analyses of mutant alleles demonstrated that one class of clones originated from the Rt locus. The rt gene has no introns and encodes a protein with homology to mammalian glucuronosyl transferases and flavonoid 3-O-glucosyl-transferase (UF3GT) encoded by the bz1 gene from Zea mays. As the Rt locus controls the rhamnosylation of reddish anthocyanin-3-O-glucosides which is the first in a series of modifications that finally yield magenta or blue/purple coloured anthocyanins, this suggests that rt encodes an anthocyanin rhamnosyl transferase.Molecular analysis of two mutant rt alleles showed that their expression is blocked by different DNA insertion elements. Mutability of the rt-vu15 allele results from the presence of a 284 bp transposable element (dTph1) in the rt promoter region, causing a block in transcription. The protein coding region of the rt-r27 allele contains a 442 bp insertion (dTph3) resulting in premature polyadenylation of rt transcripts. Although dTph3 cannot transpose, it has sequence characteristics of transposable elements, suggesting that it is a defective member of a new family of transposable elements

Patterning of Inflorescences and Flowers by the F-Box Protein DOUBLE TOP and the LEAFY Homolog ABERRANT LEAF AND FLOWER of Petunia[W]

Angiosperms display a wide variety of inflorescence architectures differing in the positions where flowers or branches arise. The expression of floral meristem identity (FMI) genes determines when and where flowers are formed. In Arabidopsis thaliana, this is regulated via transcription of LEAFY (LFY), which encodes a transcription factor that promotes FMI. We found that this is regulated in petunia (Petunia hybrida) via transcription of a distinct gene, DOUBLE TOP (DOT), a homolog of UNUSUAL FLORAL ORGANS (UFO) from Arabidopsis. Mutation of DOT or its tomato (Solanum lycopersicum) homolog ANANTHA abolishes FMI. Ubiquitous expression of DOT or UFO in petunia causes very early flowering and transforms the inflorescence into a solitary flower and leaves into petals. Ectopic expression of DOT or UFO together with LFY or its homolog ABERRANT LEAF AND FLOWER (ALF) in petunia seedlings activates genes required for identity or outgrowth of organ primordia. DOT interacts physically with ALF, suggesting that it activates ALF by a posttranslational mechanism. Our findings suggest a wider role than previously thought for DOT and UFO in the patterning of flowers and indicate that the different roles of LFY and UFO homologs in the spatiotemporal control of floral identity in distinct species result from their divergent expression patterns

FLOOZY of petunia is a flavin mono-oxygenase-like protein required for the specification of leaf and flower architecture

The mechanisms that determine the relative positions of floral organs, and thereby their numbers, is a poorly understood aspect of flower development. We isolated a petunia mutant, floozy (fzy), in which the formation of floral organ primordia in the outermost three floral whorls and one of the two bracts at the base of the flower is blocked at an early stage. In addition, fzy mutants fail to generate secondary veins in leaves and bracts and display a decreased apical dominance in the inflorescence. FZY encodes an enzyme with homology to flavin mono-oxygenases and appears to be the ortholog of YUCCA genes of Arabidopsis. FZY is expressed in young leafs and bracts and in developing flowers. In young floral meristems FZY is expressed in the center of the meristem dome and, later, expression becomes localized on the flanks of the initiating petal and stamen primordia and at several sites in maturing anthers and carpels. These findings indicate that FZY is involved in synthesizing a signaling compound that is required for floral organ initiation and specification of the vascularization pattern in leaves. Although fzy mutants contain normal auxin levels, ectopic expression of FZY results in excessive auxin accumulation, suggesting that the signaling compound is auxin

Toward the Analysis of the Petunia MADS Box Gene Family by Reverse and Forward Transposon Insertion Mutagenesis Approaches: B, C, and D Floral Organ Identity Functions Require SEPALLATA-Like MADS Box Genes in Petunia

We have initiated a systematic functional analysis of the MADS box, intervening region, K domain, C domain-type MADS box gene family in petunia. The starting point for this has been a reverse-genetics approach, aiming to select for transposon insertions into any MADS box gene. We have developed and applied a family signature insertion screening protocol that is highly suited for this purpose, resulting in the isolation of 32 insertion mutants in 20 different MADS box genes. In addition, we identified three more MADS box gene insertion mutants using a candidate-gene approach. The defined insertion lines provide a sound foundation for a systematic functional analysis of the MADS box gene family in petunia. Here, we focus on the analysis of Floral Binding Protein2 (FBP2) and FBP5 genes that encode the E-function, which in Arabidopsis has been shown to be required for B and C floral organ identity functions. fbp2 mutants display sepaloid petals and ectopic inflorescences originating from the third floral whorl, whereas fbp5 mutants appear as wild type. In fbp2 fbp5 double mutants, reversion of floral organs to leaf-like organs is increased further. Strikingly, ovules are replaced by leaf-like structures in the carpel, indicating that in addition to the B- and C-functions, the D-function, which specifies ovule development, requires E-function activity. Finally, we compare our data with results obtained using cosuppression approaches and conclude that the latter might be less suited for assigning functions to individual members of the MADS box gene family

Brassinosteroid biosynthesis and signalling in petunia hybrida

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