<Emphasis Type="Italic">AOM3</Emphasis> and<Emphasis Type="Italic"> AOM4</Emphasis>: two MADS box genes expressed in reproductive structures of<Emphasis Type="Italic"> Asparagus officinalis</Emphasis>

The MADS box genes participate in different steps of vegetative and reproductive plant development, including the most important phases of the reproductive process. Here we describe the isolation and characterisation of two Asparagus officinalis MADS box genes, AOM3 and AOM4. The deduced AOM3 protein shows the highest degree of similarity with ZAG3 and ZAG5 of maize, OsMADS6 of rice and AGL6 of Arabidopsis thaliana. The deduced AOM4 protein shows the highest degree of similarity with AOM1 of asparagus, the SEP proteins of Arabidopsis and the rice proteins OsMADS8, OsMADS45 and OsMADS7. The high level of identity between AOM1 and AOM4 made impossible the preparation of probes specific for one single gene, so the hybridisation signal previously described for AOM1 is probably due to the expression of both genes. The expression profile of AOM3 and AOM1/AOM4 during flower development is identical, and similar to that of the SEP genes. Asparagus genes, however, are expressed not only in flower organs, but also in the different meristem present on the apical region of the shoot during the flowering season: the apical meristem and the three lateral meristems emerging from the leaf axillary region that will give rise to flowers and lateral inflorescences during flowering season, and to phylloclades and branches during the subsequent vegetative phase. The expression of AOM3 and AOM1/AOM4 in these meristems appears to be correlated with the reproductive function of the apex as the hybridisation signal disappears when the apex switches to vegetative function.     

<Emphasis Type="Italic"> Cis</Emphasis>-acting elements sufficient for induction of<Emphasis Type="Italic"> FDH1</Emphasis> expression by formate in the methylotrophic yeast<Emphasis Type="Italic"> Candida boidinii</Emphasis>

The FDH1 gene of Candida boidinii encodes an NAD⁺-dependent formate dehydrogenase, which catalyzes the last reaction in the methanol dissimilation pathway. FDH1 expression is strongly induced by methanol, as are the promoters of the genes AOD1 (alcohol oxidase) and DAS1 (dihydroxyacetone synthase). FDH1 expression can be induced by formate when cells are grown on a medium containing glucose as a carbon source, whereas expression of AOD1 and DAS1 is completely repressed in the presence of glucose. Using deletion analyses, we identified two cis-acting regulatory elements, termed UAS-FM and UAS-M, respectively, in the 5 non-coding region of the FDH1 gene. Both elements were necessary for full induction of the FDH1 promoter by methanol, while only the UAS-FM element was required for full induction by formate. Irrespective of whether induction was achieved with methanol or formate, the UAS-FM element enhanced the level of induction of the FDH1 promoter in a manner dependent on the number of copies, but independent of their orientation, and also converted the ACT1 promoter from a constitutive into an inducible element. Our results not only provide a powerful promoter for heterologous gene expression, but also yield insights into the mechanism of regulation of FDH1 expression at the molecular level.Communicated by C. P. Hollenberg     

Novel mutant phenotypes of a dark-germinating mutant<Emphasis Type="Italic"> dkg1</Emphasis> in the fern<Emphasis Type="Italic"> Ceratopteris richardii</Emphasis>

The mutant dark-germinating 1 (dkg1) of the fern Ceratopteris richardii was originally characterized by two phenotypes, germination in the dark and inhibition of germination by light. In this work, we examined whether other phenotypes are present in the gametophytic generation of the dkg1 mutant. Although dkg1 prothalli grown in darkness were elongated as in the case of the wild type, some developmental processes were found to proceed even in complete darkness: (1) the apical and subapical zones developed largely by forming a lateral meristem; (2) asymmetric cell division for rhizoid differentiation occurred in the subapical elongation zone; (3) an archegonium was formed in the proximity of the meristem; and (4) chloroplast relocation could occur without de novo protein synthesis. Furthermore, these processes were shown to be under the control of phytochrome in the wild-type gametophytes on the basis of red/far-red reversibility. These results indicate that the DKG1 gene is pleiotropic and is involved in several phytochrome-mediated responses in the gametophyte development of C. richardii.     

The white-phase-specific gene<Emphasis Type="Italic"> WH11</Emphasis> is not required for white-opaque switching in<Emphasis Type="Italic"> Candida albicans</Emphasis>

Phenotypic switching between white and opaque cells is important for adaptation to different host environments and for mating in the opportunistic fungal pathogen Candida albicans. Genes that are specifically activated in one of the two cell types are likely to be important for their phenotypic characteristics. The WH11 gene is a white-phase-specific gene that has been suggested to be involved in the maintenance of the white-phase phenotype. To elucidate the role of WH11 in white-opaque switching, we constructed mutants of the C. albicans strain WO-1 in which the WH11 gene was deleted. The wh11 mutants were still able to form both white and opaque cells whose cellular and colony phenotypes were indistinguishable from those of the wild type. Deletion of WH11 also did not affect the activation and deactivation of the white-phase-specific WH11 promoter and the opaque-phase-specific OP4 and SAP1 promoters in the appropriate cell type. Finally, switching from the white to the opaque phase and vice versa occurred with the same frequency in wild-type and wh11 mutants. Therefore, the WH11 gene is not required for phenotypic switching, and its protein product seems to have other roles in white cells, which are dispensable after the switch to the opaque phase.Communicated by E. Cerdá-Olmedo     

Nucleosome transactions on the<Emphasis Type="Italic"> Hypocrea jecorina</Emphasis> (<Emphasis Type="Italic"> Trichoderma reesei</Emphasis>) cellulase promoter<Emphasis Type="Italic"> cbh2</Emphasis> associated with cellulase induction

The 5 regulatory region of the cbh2 gene of Hypocrea jecorina contains the cbh2 activating element (CAE) which is essential for induction of cbh2 gene expression by sophorose and cellulose. The CAE consists of two motifs, a CCAAT box on the template strand and a GTAATA box on the coding strand, which cooperate during induction. Northern analyses of cbh2 gene expression has revealed an absolute dependence on induction, but no direct effect of Cre1-mediated carbon catabolite repression. Investigation of the chromatin structure in the wild-type strain showed that, under repressing conditions, there is a nucleosome free region (nfr) around the CAE, which is flanked by strictly positioned nucleosomes. Induction results in a loss of positioning of nucleosomes –1 and –2 downstream of the CAE, thus making the TATA box accessible. Simultaneous mutation of both motifs of the CAE, or of the CCAAT-box alone, also leads to shifting of nucleosome –1, which normally covers the TATA-box under repressing conditions, whereas mutation of the GTAATA element results in a narrowing of the nfr, indicating that the proteins that bind to both motifs in the CAE interact with chromatin, although in different ways. A cellulase-negative mutant strain, which has previously been shown to be altered in protein binding to the CAE, still displayed the induction-specific changes in nucleosome structure, indicating that none of the proteins that directly interact with CAE are affected, and that nucleosome rearrangement and induction of cbh2 expression are uncoupled. Interestingly, the carbon catabolite repressor Cre1 is essential for strict nucleosome positioning in the 5 regulatory sequences of cbh2 under all of the conditions tested, and induction can occur in a promoter that lacks positioned nucleosomes. These data suggest that Cre1, the Hap2/3/5 complex and the GTAATA-binding protein are all involved in nucleosome assembly on the cbh2 promoter, and that the latter two respond to inducing conditions by repositioning nucleosome –1.Communicated by C. A. M. J. J. van den Hondel     

The<Emphasis Type="Italic"> GAOLAOZHUANGREN2</Emphasis> gene is required for normal glucose response and development of<Emphasis Type="Italic"> Arabidopsis</Emphasis>

Recent studies of glucose (Glc) sensing and signaling have revealed that Glc acts as a critical signaling molecule in higher plants. Several Glc sensing-defective Arabidopsis mutants have been characterized in detail, and the corresponding genes encoding Glc-signaling proteins have been isolated. However, the full complexity of Glc signaling in higher plants is not yet fully understood. Here, we report the identification and characterization of a new Glc-insensitive mutant, gaolaozhuangren2 (glz2), which was isolated from transposon mutagenesis experiments in Arabidopsis. In addition to its insensitivity to Glc, the glz2 plant exhibits several developmental defects such as short stature with reduced apical dominance, short roots, small and dark-green leaves, late flowering and female sterility. Treatment with 4% Glc blocked expression of the OE33 gene in wild-type plants, whereas expression of this gene was unchanged in the glz2 mutant plants. Taken together, our results suggest that the GLZ2 gene is required for normal glucose response and development of Arabidopsis.Mingjie Chen and Xiaoxiang Xia contributed equally to this work.     

Expression of<Emphasis Type="Italic"> ENOD40</Emphasis> during tomato plant development

In legumes, ENOD40 expression is increased upon interaction of plants with rhizobia. Little is known of the expression pattern of ENOD40 during other stages of the plant life cycle. Studies of ENOD40 expression in non-legume development may give an indication of the function of the gene. To investigate the ENOD40 expression pattern during plant development, a fusion between the -glucuronidase (GUS) reporter gene and 150 bp of the 5 untranslated region plus 3,000 bp of 5 untranscribed tomato ENOD40 sequence was constructed and introduced into Lycopersicon esculentum Miller. Based on the observed GUS expression patterns in transgenic tomato we speculate that ENOD40 in tomato has a role in counteracting ethylene-provoked responses.Abbreviations GUS -glucuronidase - FISH fluorescence in situ hybridisation - RACE rapid amplification of cDNA ends - RFLC restriction fragment length polymorphism     

Developmental anatomy of the fifth shoot-borne root in young sporophytes of<Emphasis Type="Italic"> Ceratopteris richardii</Emphasis>

Young sporophytes of the homosporous fern Ceratopteris richardii produce a single shoot-borne root below each leaf. The developmental anatomy of the fifth sporophyte root is described using scanning electron microscopy and histological techniques. Three merophyte orthostichies in the body of the root originate from three proximal division faces of a tetrahedral root apical cell. Eight or nine divisions occur in a relatively regular sequence within each merophyte and produce a characteristic radial anatomical pattern in the root. The exact number of early divisions within a merophyte depends on the merophytes position within the root as a whole. Predictable inter-merophyte differences arise because a 2-fold (diarch) anatomical symmetry that is characteristic of mature roots is superimposed on a 3-fold radial symmetry that originates behind the apical cell. Before early formative divisions within a merophyte are completed, additional proliferative divisions begin to increase the number of cells within previously established tissue zones. The cellular parameters of early fifth root development in C. richardii are relatively invariant, and are reminiscent of patterns previously described for the heterosporous fern Azolla. Young sporophytes of C. richardii provide a useful model to further investigate the genetic regulation of root development in a non-seed plant, where the anatomy of meristem organization differs from that seen in flowering plant species.Abbreviations SEM Scanning electron microscopy - RAC Root apical cell     

Intergeneric conjugal transfer of plasmid DNA from<Emphasis Type="Italic"> Escherichia coli</Emphasis> to<Emphasis Type="Italic"> Kitasatospora setae</Emphasis>, a bafilomycin B<Subscript>1</Subscript> producer

An effective transformation procedure for Kitasatospora setae was established based on transconjugation from Escherichia coli ET12567 (pUZ8002) using a C31-derived integration vector, pSET152, containing oriT and attP fragments. While no transconjugation was observed under the standard transconjugation conditions for Streptomyces species, sufficient transconjugation (>1×10^-6) was achieved on ISP4 medium containing 30 mM MgCl₂ using a 25- to 125-fold excess of E. coli donor cells. In addition, the sequence and location of the chromosomal integration site attB of K. setae was identified for the first time in genera of non-Streptomyces actinomycetes. K. setae contains a single C31 attB site. Similar to the case of Streptomyces species, the attB site of K. setae is present within an ORF encoding a pirin-homolog, but the K. setae-attB sequence deviates slightly from the consensus sequence of Streptomyces attB sequences.     

<Emphasis Type="Italic">WUS</Emphasis> and <Emphasis Type="Italic">STM</Emphasis> homologs are linked to the expression of lateral dominance in the acaulescent <Emphasis Type="Italic">Streptocarpus rexii</Emphasis> (Gesneriaceae)

Acaulescent species of Streptocarpus Lindl. show unusual patterns of growth, characterized by anisocotyly (i.e. the unequal growth of cotyledons after germination) and lack of a conventional embryonic shoot apical meristem (SAM). A SAM-like structure appears during post-embryonic development on the axis of the continuously growing cotyledon. Since we have shown previously that KNOX genes are involved in this unusual morphology of Streptocarpus rexii, here we investigated the expression pattern of WUSCHEL (WUS), which is also required for the indeterminacy of the SAM, but is expressed independently from KNOX in Arabidopsis thaliana. In A. thaliana WUSCHEL is involved in the maintenance of the stem cell fate in the organizing centre. The expression pattern of the WUS ortholog in S. rexii (SrWUS) strongly deviates from that of the model plant, suggesting a fundamentally different spatial and temporal regulation of signalling involved in meristem initiation and maintenance. In S. rexii, exogenous application of growth regulators, i.e. gibberellin (GA₃), cytokinin (CK) and a gibberellin biosynthesis inhibitor (PAC), prevents anisocotyly and relocates meristematic cells to a position of conventional SAMs; this coincides with a re-localization of the two main pathways controlling meristem formation, the SrWUS and the KNOX pathways. Our results suggest that the establishment of a hormone imbalance in the seedlings is the basis of anisocotyly, causing a lateral dominance of the macrocotyledon over the microcotyledon. The peculiar morphogenetic program in S. rexii is linked to this delicate hormone balance and is the result of crosstalk between endogenous hormones and regulatory genes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-<Emphasis Type="Italic">tumefaciens</Emphasis>-mediated transformation of<Emphasis Type="Italic"> Helminthosporium turcicum</Emphasis>, the maize leaf-blight fungus

Agrobacterium tumefaciens has the ability to transfer its T-DNA to plants, yeast, filamentous fungi, and human cells and integrate it into their genome. Conidia of the maize pathogen Helminthosporium turcicum were transformed to hygromycin B resistance by a Agrobacterium-tumefaciens-mediated transformation system using a binary plasmid vector containing the hygromycin B phosphotransferase (hph) and the enhanced green fluorescent protein (EGFP) genes controlled by the gpd promoter from Agaricus bisporus and the CaMV 35S terminator. Agrobacterium-tumefaciens-mediated transformation yielded stable transformants capable of growing on increased concentrations of hygromycin B. The presence of hph in the transformants was confirmed by PCR, and integration of the T-DNA at random sites in the genome was demonstrated by Southern blot analysis. Agrobacterium-tumefaciens-mediated transformation of Helminthosporium turcicum provides an opportunity for advancing studies of the molecular genetics of the fungus and of the molecular basis of its pathogenicity on maize.     

An improved,simple, hydroponic method for growing<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Arabidopsis thaliana is one os the most studied plant model systems. Completing the genomic sequence ofA. thaliana has provided new opportunities for physiological and biochemical studies. While its small size is advantageous for genetic studies, the plant's low biomass makes it difficult to obtain enough plant material for biochemical and physiological research. The small size and rosette leaf structure, combined with the sensitivity of the apical meristem to flooding, make hydroponic growth of this model plant difficult. A few systems for hydroponic culture ofArabidopsis have been described. Gibeaut et al. (1997) introduced the use of rockwool forArabidopsis hydroponic culture. We have improved this system by introducing small-volume plastic containers with improved plugs to support the rockwool. This method is simpler than the original setup and provides improved germination and growth. The smaller containers enable the use of this system in growth chambers or small growth rooms for a large number of parallel experiments.     

The pea<Emphasis Type="Italic"> END1</Emphasis> promoter drives anther-specific gene expression in different plant species

END1 was isolated by an immunosubtractive approach intended to identify specific proteins present in the different pea (Pisum sativum L.) floral organs and the genes encoding them. Following this strategy we obtained a monoclonal antibody (mAbA1) that specifically recognized a 26-kDa protein (END1) only detected in anther tissues. Northern blot assays showed that END1 is expressed specifically in the anther. In situ hybridization and immunolocalization assays corroborated the specific expression of END1 in the epidermis, connective, endothecium and middle layer cells during the different stages of anther development. END1 is the first anther-specific gene isolated from pea. The absence of a practicable pea transformation method together with the fact that no END1 homologue gene exists in Arabidopsis prevented us from carrying out END1 functional studies. However, we designed functional studies with the END1 promoter in different dicot species, as the specific spatial and temporal expression pattern of END1 suggested, among other things, the possibility of using its promoter region for biotechnological applications. Using different constructs to drive the uidA (-glucuronidase) gene controlled by the 2.7-kb isolated promoter sequence we have proven that the END1 promoter is fully functional in the anthers of transgenic Arabidopsis thaliana (L.) Heynh., Nicotiana tabacum L. (tobacco) and Lycopersicon esculentum Mill. (tomato) plants. The presence in the –330-bp region of the promoter sequence of three putative CArG boxes also suggests that END1 could be a target gene of MADS-box proteins and that, subsequently, it would be activated by genes controlling floral organ identity.Abbreviations GUS -Glucuronidase - uidA -Glucuronidase gene - Nos Nopaline synthase gene - nptII Neomycin phosphotransferase II gene - SEM Scanning electron microscopy GenBank accession numbers for the END1 cDNA and the END1 promoter: AY 091466 and AY 324651, respectively     

Development of genotype-independent regeneration system for transformation of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> ssp. <Emphasis Type="Italic">indica</Emphasis>)

Rice (Oryza sativa ssp. indica) is an important economic crop in many countries. Although a variety of conventional methods have been developed to improve this plant, manipulation by genetic engineering is still complicated. We have established a system of multiple shoot regeneration from rice shoot apical meristem. By use of MS medium containing 4 mg L⁻¹ thidiazuron (TDZ) multiple shoots were successfully developed directly from the meristem without an intervening callus stage. All rice cultivars tested responded well on the medium and regenerated to plantlets that were readily transferred to soil within 5–8 weeks. The tissue culture system was suitable for Agrobacterium-mediated transformation and different factors affecting transformation efficiency were investigated. Agrobacterium strain EHA105 containing the plasmid pCAMBIA1301 was used. The lowest concentration of hygromycin B in combined with either 250 mg L⁻¹ carbenicillin or 250 mg L⁻¹ cefotaxime to kill the rice shoot apical meristem was 50 mg L⁻¹ and carbenicillin was more effective than cefotaxime. Two-hundred micromolar acetosyringone had no effect on the efficiency of transient expression. Sonication of rice shoot apical meristem for 10 s during bacterial immersion increased transient GUS expression in three-day co-cultivated seedlings. The gus gene was found to be integrated into the genome of the T₀ transformant plantlets.     

Molecular genetics of the<Emphasis Type="Italic"> Alhambra</Emphasis> (<Emphasis Type="Italic"> Drosophila AF10</Emphasis>) complex locus of<Emphasis Type="Italic"> Drosophila</Emphasis>

The Alhambra ( Alh) gene is the Drosophila homologue of the human AF10 gene. AF10 has been identified as a fusion partner of MLL, a human homologue of the fly gene trithorax, in infant leukemias. The endogenous function of human AF10 is not known, but may be vital to its role in acute leukemia. This prompted us to analyse Alh function. We describe here the genetic organisation of the Alh locus in D. melanogaster. We show that an independent lethal complementation group encoding a muscle protein ( Mlp84B) is located within an Alh intron. We have already shown that the leucine zipper (LZ) domain of ALH activates several Polycomb group-responsive elements. We further demonstrate that the LZ domain on its own bears the Alh vital function, since it is necessary and sufficient for rescue of Alh mutant lethality. Finally, we demonstrate that, in contrast to a previous report, Alh does not affect position-effect variegation.Communicated by G. Reuter     

<Emphasis Type="Italic">MIR166</Emphasis>/<Emphasis Type="Italic">165</Emphasis> genes exhibit dynamic expression patterns in regulating shoot apical meristem and floral development in <Emphasis Type="Italic">Arabidopsis</Emphasis>

The miR166/165 group and its target genes regulate diverse aspects of plant development, including apical and lateral meristem formation, leaf polarity, and vascular development. We demonstrate here that MIR166/165 genes are dynamically controlled in regulating shoot apical meristem (SAM) and floral development in parallel to the WUSCHEL (WUS)-CLAVATA (CLV) pathway. Although miR166 and miR165 cleave same target mRNAs, individual MIR166/165 genes exhibit distinct expression domains in different plant tissues. The MIR166/165 expression is also temporarily regulated. Consistent with the dynamic expression patterns, an array of alterations in SAM activities and floral architectures was observed in the miR166/165-overproducing plants. In addition, when a MIR166a-overexpressing mutant was genetically crossed with mutants defective in the WUS-CLV pathway, the resultant crosses exhibited additive phenotypic effects, suggesting that the miR166/165-mediated signal exerts its role via a distinct signaling pathway.     

Analyses of<Emphasis Type="Italic"> cis</Emphasis> -acting elements that affect the transposition of<Emphasis Type="Italic"> Mos1 mariner</Emphasis> transposons in vivo

The left (5) inverted terminal repeat (ITR) of the Mos1 mariner transposable element was altered by site-directed mutagenesis so that it exactly matched the nucleotide sequence of the right (3) ITR. The effects on the transposition frequency resulting from the use of two 3 ITRs, as well as those caused by the deletion of internal portions of the Mos1 element, were evaluated using plasmid-based transposition assays in Escherichia coli and Aedes aegypti. Donor constructs that utilized two 3 ITRs transposed with greater frequency in E. coli than did donor constructs with the wild-type ITR configuration. The lack of all but 10 bp of the internal sequence of Mos1 did not significantly affect the transposition frequency of a wild-type ITR donor. However, the lack of these internal sequences in a donor construct that utilized two 3 ITRs resulted in a further increase in transposition frequency. Conversely, the use of a donor construct with two 3 ITRs did not result in a significant increase in transposition in Ae. aegypti. Furthermore, deletion of a large portion of the internal Mos1 sequence resulted in the loss of transposition activity in the mosquito. The results of this study indicate the possible presence of a negative regulator of transposition located within the internal sequence, and suggest that the putative negative regulatory element may act to inhibit binding of the transposase to the left ITR. The results also indicate that host factors which are absent in E. coli, influence Mos1 transposition in Ae. aegypti.Communicated by G. P. Georgiev     

Use of gain-of-function study to delineate the roles of<Emphasis Type="Italic">crumbs</Emphasis> in<Emphasis Type="Italic">Drosophila</Emphasis> eye development

The cell polarity gene,crumbs (crb), has been shown to participate in the development and degeneration of theDrosophila retina. Mutations inCRB1, the human homologue ofDrosophila crb, also result in retinitis pigmentosa and Leber congential amaurosis. In this study, we used the gain-of-function approach to delineate the roles ofcrb in developingDrosophila eye. In the third-instar larval stage, eye development is initiated with photoreceptor differentiation and positioning of photoreceptor nuclei in the apical cellular compartment of retinal epithelium. In the pupal stage, differentiated photoreceptors begin to form the photosensitive structures, the rhabdomeres, at their apical surface. UsingGMR-Gal4 to drive overexpression of the Crb protein at the third-instar eye disc, we found that differentiation of photoreceptors was disrupted and the nuclei of differentiated photoreceptors failed to occupy the apical compartment. Usinghs-Gal4 to drive Crb overexpression in pupal eyes resulted in interference with extension of the adherens junctions and construction of the rhabdomeres, and these defects were stage-dependent. This gain-of-function study has enabled us to delineate the roles of Crb at selective stages of eye development inDrosophila.     

Altered expression of the<Emphasis Type="Italic"> Arabidopsis</Emphasis> ortholog of<Emphasis Type="Italic"> DCL</Emphasis> affects normal plant development

The DCL (defective chloroplasts and leaves) gene of tomato (Lycopersicon esculentum Mill.) is required for chloroplast development, palisade cell morphogenesis, and embryogenesis. Previous work suggested that DCL protein is involved in 4.5S rRNA processing. The Arabidopsis thaliana (L.) Heynh. genome contains five sequences encoding for DCL-related proteins. In this paper, we investigate the function of AtDCL protein, which shows the highest amino acid sequence similarity with tomato DCL. AtDCL mRNA was expressed in all tissues examined and a fusion between AtDCL and green fluorescent protein (GFP) was sufficient to target GFP to plastids in vivo, consistent with the localization of AtDCL to chloroplasts. In an effort to clarify the function of AtDCL, transgenic plants with altered expression of this gene were constructed. Deregulation of AtDCL gene expression caused multiple phenotypes such as chlorosis, sterile flowers and abnormal cotyledon development, suggesting that this gene is required in different organs. The processing of the 4.5S rRNA was significantly altered in these transgenic plants, indicating that AtDCL is involved in plastid rRNA maturation. These results suggest that AtDCL is the Arabidopsis ortholog of tomato DCL, and indicate that plastid function is required for normal plant development.Abbreviations DCL Defective chloroplasts and leaves - GFP Green fluorescent protein     

Phenotypic alterations in<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis> plants caused by<Emphasis Type="Italic"> Rhodococcus fascians</Emphasis> infection

Arabidopsis thaliana (L.) Heynh. plants were challenged with Rhodococcus fascians at several developmental stages and using different inoculation procedures. A variety of morphological alterations was scored on the infected plants; some of them resembled phenotypes of A. thaliana mutants in their shoot apical meristem (SAM) organization. Infection with R. fascians did not affect SAM organization in wild type nor in SAM mutants. Anatomical studies on the new organs formed after infection with R. fascians demonstrated extensive bacterial colonization. Colonization and concomitant production of specific signals are the likely cause of malformations.