<Emphasis Type="Italic">APETALA2</Emphasis> like genes from <Emphasis Type="Italic">Picea abies</Emphasis> show functional similarities to their Arabidopsis homologues

In angiosperm flower development the identity of the floral organs is determined by the A, B and C factors. Here we present the characterisation of three homologues of the A class gene APETALA2 (AP2) from the conifer Picea abies (Norway spruce), Picea abies APETALA2 LIKE1 (PaAP2L1), PaAP2L2 and PaAP2L3. Similar to AP2 these genes contain sequence motifs complementary to miRNA172 that has been shown to regulate AP2 in Arabidopsis. The genes display distinct expression patterns during plant development; in the female-cone bud PaAP2L1 and PaAP2L3 are expressed in the seed-bearing ovuliferous scale in a pattern complementary to each other, and overlapping with the expression of the C class-related gene DAL2. To study the function of PaAP2L1 and PaAP2L2 the genes were expressed in Arabidopsis. The transgenic PaAP2L2 plants were stunted and flowered later than control plants. Flowers were indeterminate and produced an excess of floral organs most severely in the two inner whorls, associated with an ectopic expression of the meristem-regulating gene WUSCHEL. No homeotic changes in floral-organ identities occurred, but in the ap2-1 mutant background PaAP2L2 was able to promote petal identity, indicating that the spruce AP2 gene has the capacity to substitute for an A class gene in Arabidopsis. In spite of the long evolutionary distance between angiosperms and gymnosperms and the fact that gymnosperms lack structures homologous to sepals and petals our data supports a functional conservation of AP2 genes among the seed plants.     

Expression of the glutathione <Emphasis Type="Italic">S</Emphasis>-transferase gene (NT107) in transgenic <Emphasis Type="Italic">Dianthus superbus</Emphasis>

Using an Agrobacterium-mediated transformation method based on wounding cultured immature seeds with carborundum (600 mesh) in liquid, auxin-regulated tobacco glutathione S -transferase (GST) (NT107) constructs were used to transform Dianthus superbusL. A 663 bp DNA band was found in the transgenic plant genome by PCR analysis using NT107-1 and NT107-2 primers, and a Southern blot analysis showed that the DIG-labelled GST gene was hybridized to the expected amplified genomic DNA fragment from transgenic D. superbus. An overexpression of NT107 led to a twofold increase in GST-specific activity compared to the non-transgenic control plants, and the GST overexpression plants showed an enhanced acclimatization in the soil. To investigate whether an increased expression of GST could affect the resistance of photosynthesis to environmental stress, these plants were subjected to drought and various light intensities from 100 to 3000 mol m^–2s^–1. Copper accumulation and the translocation rate were also analysed in the transgenic lines, and the GST overexpression plants were found to synthesize phytochelatin (PC), which functions by sequestering and detoxifying excess copper ions.These two authors contributed equally to this work     

<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> plants overexpressing <Emphasis Type="Italic">Ramosa1</Emphasis> maize gene show an increase in organ size due to cell expansion

The structure of the plant inflorescence and flower is an important agronomic and ornamental trait studied for its potential economic applications. In particular, the capacity to modify flower size has always been a breeder’s goal. Genetic and molecular studies have shown that the Zea mays gene Ramosa1 (Ra1) is involved in inflorescence branching regulation. In fact the ra1 loss of function mutation causes extra branching of the inflorescence. In this work we suggest a possible utilization of the Ramosa1 maize gene as a tool to modify inflorescence architecture and flower size in transgenic plants. In fact overexpression of this gene in Arabidopsis plants promotes an increase in reproductive organ size. Pollen, seeds, cotyledons, leaves and roots are also larger than those of the wild type. Analysis of organs from transformants showed that cell expansion was increased without apparently affecting cell division. These results suggest that the RA1 protein is able to up-regulate cell expansion in all organs of Arabidopsis plants.     

Improved phosphate metabolism and biomass production by overexpression of <Emphasis Type="Italic">AtPAP18</Emphasis> in tobacco

Limited availability of phosphate ion (Pi) reduces plant growth in natural ecosystems. Here, we report the functional effects of overexpressing an Arabidopsis thaliana purple acid phosphatase encoding gene, AtPAP18, in Nicotiana tabbacum as a crop model plant. Transgenic tobacco plants exhibited significant increases in acid phosphatase activity, total P and Pi contents leading to improved biomass production in both Pi-deficient and Pi-sufficient conditions. Transient expression of AtPAP18::green fluorescent fusion protein in onion epidermal cells indicated that AtPAP18 is a dual-targeted protein, which is detected mainly in the apoplast of the cells after 24 h and in the vacuole after 72 h. Possibly, AtPAP18 protein confers efficient retrieval of Pi from bonded extracellular compounds as well as expendable intracellular Pi-monoesters and anhydrides. These data clearly indicate that overexpression of AtPAP18 gene offers an effective approach for reducing the consumption of chemical Pi fertilizer through increased acquisition of soil Pi and mobilization of internal resources.     

<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.     

A rice <Emphasis Type="Italic">YABBY</Emphasis> gene, <Emphasis Type="Italic">OsYABBY4</Emphasis>, preferentially expresses in developing vascular tissue

Developmental gene families have diversified during land plant evolution. The primary role of YABBY gene family is promoting abaxial fate in model eudicot, Arabidopsis thaliana. However recent results suggest that roles of YABBY genes are not conserved in the angiosperms. In this paper, a rice YABBY gene was isolated, and its expression patterns were analyzed in detail. Sequence characterization and phylogenetic analyses showed the gene is OsYABBY4, which is group-classified into FIL/YAB3 subfamily. Beta-glucuronidase reporter assay and in situ analysis consistently revealed that OsYABBY4 was expressed in the meristems and developing vascular tissue of rice, predominantly in the phloem tissue, suggesting that the function of the rice gene is different from those of its counterparts in eudicots. OsYABBY4 may have been recruited to regulate the development of vasculature in rice. However, transgenic Arabidopsis plants ectopically expressing OsYABBY4 behaved very like those over-expressing FIL or YAB3 with abaxialized lateral organs, suggesting the OsYABBY4 protein domain is conserved with its Arabidopsis counterparts in sequences. Our results also indicate that the functional diversification of OsYABBY4 may be associated with the divergent spatial-temporal expression patterns, and YABBY family members may have preserved different expression regulatory systems and functions during the evolution of different kinds of species.     

Isolation and characterization of the <Emphasis Type="Italic">Larix gmelinii </Emphasis><Emphasis Type="Italic">ANGUSTIFOLIA</Emphasis> (<Emphasis Type="Italic">LgAN</Emphasis>) gene

ANGUSTIFOLIA (AN), a plant homolog of C-terminal binding protein, controls the polar elongation of leaf cells and the trichome-branching pattern in Arabidopsis thaliana. In the present study, degenerate PCR was used to isolate an ortholog of AN, referred to as LgAN, from larch (Larix gmelinii). The LgAN cDNA is predicted to encode a protein of 646 amino acids that shows striking sequence similarity to AN proteins from other plants. The predicted amino acid sequence has a conserved NAD-dependent 2-hydroxy acid dehydrogenase (D2-HDH) motif and a plant AN-specific LxCxE/D motif at its N-terminus, as well as a plant-specific long C-terminal region. The LgAN gene is a single-copy gene that is expressed in all larch tissues. Expression of the LgAN cDNA rescued the leaf width and trichome-branching pattern defects in the angustifolia-1 (an-1) mutant of Arabidopsis, showing that the LgAN gene has effects complementary to those of AN. These results suggest that the LgAN gene has the same function as the AN gene.     

Molecular characterization the <Emphasis Type="Italic">YABBY</Emphasis> gene family in <Emphasis Type="Italic">Oryza sativa</Emphasis> and expression analysis of <Emphasis Type="Italic">OsYABBY1</Emphasis>

Members of the YABBY gene family have a general role that promotes abaxial cell fate in a model eudicot, Arabidopsis thaliana. To understand the function of YABBY genes in monocots, we have isolated all YABBY genes in Oryza sativa (rice), and revealed the spatial and temporal expression pattern of one of these genes, OsYABBY1. In rice, eight YABBY genes constitute a small gene family and are classified into four groups according to sequence similarity, exon-intron structure, and organ-specific expression patterns. OsYABBY1 shows unique spatial expression patterns that have not previously been reported for other YABBY genes, so far. OsYABBY1 is expressed in putative precursor cells of both the mestome sheath in the large vascular bundle and the abaxial sclerenchyma in the leaves. In the flower, OsYABBY1 is specifically expressed in the palea and lemma from their inception, and is confined to several cell layers of these organs in the later developmental stages. The OsYABBY1-expressing domains are closely associated with cells that subsequently differentiate into sclerenchymatous cells. These findings suggest that the function of OsYABBY1 is involved in regulating the differentiation of a few specific cell types and is unrelated to polar regulation of lateral organ development.