Using Multiplexed CRISPR/Cas9 for Suppression of Cotton Leaf Curl Virus

In recent decades, Pakistan has suffered a decline in cotton production due to several factors, including insect pests, cotton leaf curl disease (CLCuD), and multiple abiotic stresses. CLCuD is a highly damaging plant disease that seriously limits cotton production in Pakistan. Recently, genome editing through CRISPR/Cas9 has revolutionized plant biology, especially to develop immunity in plants against viral diseases. Here we demonstrate multiplex CRISPR/Cas-mediated genome editing against CLCuD using transient transformation in N. benthamiana plants and cotton seedlings. The genomic sequences of cotton leaf curl viruses (CLCuVs) were obtained from NCBI and the guide RNA (gRNA) were designed to target three regions in the viral genome using CRISPR MultiTargeter. The gRNAs were cloned in pHSE401/pKSE401 containing Cas9 and confirmed through colony PCR, restriction analysis, and sequencing. Confirmed constructs were moved into Agrobacterium and subsequently used for transformation. Agroinfilteration in N. benthamiana revealed delayed symptoms (3–5 days) with improved resistance against CLCuD. In addition, viral titer was also low (20–40%) in infected plants co-infiltrated with Cas9-gRNA, compared to control plants (infected with virus only). Similar results were obtained in cotton seedlings. The results of transient expression in N. benthamiana and cotton seedlings demonstrate the potential of multiplex CRISPR/Cas to develop resistance against CLCuD. Five transgenic plants developed from three experiments showed resistance (60−70%) to CLCuV, out of which two were selected best during evaluation and screening. The technology will help breeding CLCuD-resistant cotton varieties for sustainable cotton production.

Differential Gene Expression with an Emphasis on Floral Organ Size Differences in Natural and Synthetic Polyploids of Nicotiana tabacum (Solanaceae)

Floral organ size, especially the size of the corolla, plays an important role in plant reproduction by facilitating pollination efficiency. Previous studies have outlined a hypothesized organ size pathway. However, the expression and function of many of the genes in the pathway have only been investigated in model diploid species; therefore, it is unknown how these genes interact in polyploid species. Although correlations between ploidy and cell size have been shown in many systems, it is unclear whether there is a difference in cell size between naturally occurring and synthetic polyploids. To address these questions comparing floral organ size and cell size across ploidy, we use natural and synthetic polyploids of Nicotiana tabacum (Solanaceae) as well as their known diploid progenitors. We employ a comparative transcriptomics approach to perform analyses of differential gene expression, focusing on candidate genes that may be involved in floral organ size, both across developmental stages and across accessions. We see differential expression of several known floral organ candidate genes including ARF2, BIG BROTHER, and GASA/GAST1. Results from linear models show that ploidy, cell width, and cell number positively influence corolla tube circumference; however, the effect of cell width varies by ploidy, and diploids have a significantly steeper slope than both natural and synthetic polyploids. These results demonstrate that polyploids have wider cells and that polyploidy significantly increases corolla tube circumference.

Ontogenetic shift from aposematism and gregariousness to crypsis in a Romaleid grasshopper

Traits of chemically-defended animals can change as an individual grows and matures, and both theoretical and empirical evidence favour a direction of change from crypsis to aposematism. This study examines the suite of traits involved in an unusual opposite shift from aposematism to crypsis in a neotropical toxic-plant-feeding Romaleid grasshopper, Chromacris psittacus (Gerstaecker, 1873). Field surveys, behavioural observations and a rearing experiment compare host plant choice, aggregation, locomotion and thermoregulation between life history stages. Results showed that both nymphs and adults fed exclusively on a narrow range of Solanaceae plants, suggesting that the shift in defensive syndrome is not due to a change in chemical defense. Instead, nymphal aposematism appears linked to aggregation in response to plant-based selection pressures. Slow nymphal development suggests a cost to feeding on toxic plant compounds, and grouping could mitigate this cost. Grouping also increases conspicuousness, and hence can favour warning colourating in chemically-defended insects. The role of diet breadth in aposematism is poorly understood, and these results suggest how constraints imposed by feeding on toxic plants can generate bottom-up selection pressures shaping the adaptive suites of traits of chemically-defended animals.

Effects of living hyperaccumulator plants and their straws on the growth and cadmium accumulation of Cyphomandra betacea seedlings

To determine whether the living hyperaccumulator plants and their straws have the same effects on the growth and heavy metal accumulation of common plants, two pot experiments (intercropping experiment and straw mulch experiment) were conducted to study the effects of living hyperaccumulator plants (Solanum photeinocarpum, Tagetes erecta, Galinsoga parviflora and Bidens pilosa) and their straws on the growth and cadmium (Cd) accumulation of common plant Cyphomandra betacea seedlings. Intercropping with T. erecta or B. pilosa promoted the growth of C. betacea seedlings compared with the monoculture, while intercropping with S. photeinocarpum or G. parviflora inhibited that. Intercropping with S. photeinocarpum decreased the Cd contents in the roots and shoots of C. betacea seedlings compared with the monoculture, but intercropping with the other plants did not. In the straw mulch experiment, the straw of S. photeinocarpum or T. erecta promoted the growth of C. betacea seedlings compared with the control, while the straw of G. parviflora or B. pilosa did not. The straw of S. photeinocarpum or T. erecta decreased the Cd contents in the shoots of C. betacea seedlings, and the straw of G. parviflora or B. pilosa increased the shoot Cd contents. Thus, intercropping with S. photeinocarpum and applying S. photeinocarpum or T. erecta straw can reduce the Cd uptake of C. betacea.

Evolution of genes associated with gynoecium patterning and fruit development in Solanaceae

BACKGROUND AND AIMS

The genetic basis of fruit development has been extensively studied in Arabidopsis, where major transcription factors controlling valve identity (i.e. FRUITFULL), replum development (i.e. REPLUMLESS) and the differentiation of the dehiscence zones (i.e. SHATTERPROOF, INDEHISCENT and ALCATRAZ) have been identified. This gene regulatory network in other flowering plants is influenced by duplication events during angiosperm diversification. Here we aim to characterize candidate fruit development genes in the Solanaceae and compare them with those of Brassicaceae.

METHODS

ALC/SPT, HEC/IND, RPL and AG/SHP homologues were isolated from publicly available databases and from our own transcriptomes of Brunfelsia australis and Streptosolen jamesonii. Maximum likelihood phylogenetic analyses were performed for each of the gene lineages. Shifts in protein motifs, as well as expression patterns of all identified homologues, are shown in dissected floral organs and fruits in different developmental stages of four Solanaceae species exhibiting different fruit types.

KEY RESULTS

Each gene lineage has undergone different duplication time-points, resulting in very different genetic complements in the Solanaceae when compared with the Brassicaceae. In general, Solanaceae species have more copies of HEC1/2 and RPL than Brassicaceae, have fewer copies of SHP and the same number of copies of AG, ALC and SPT. Solanaceae lack IND orthologues, but have pre-duplication HEC3 homologues. The expression analyses showed opposite expression of SPT and ALC orthologues between dry- and fleshy-fruited species during fruit maturation. Fleshy-fruited species turn off RPL and SPT orthologues during maturation.

CONCLUSIONS

The gynoecium patterning and fruit developmental genetic network in the Brassicaceae cannot be directly extrapolated to the Solanaceae. In Solanaceae ALC, SPT and RPL contribute differently to maturation of dry dehiscent and fleshy fruits, whereas HEC genes are not generally expressed in the gynoecium. RPL genes have broader expression patterns than expected.

Plant reference genes for development and stress response studies

Many reference genes are used by different laboratories for gene expression analyses to indicate the relative amount of input RNA/DNA in the experiment. These reference genes are supposed to show least variation among the treatments and with the control sets in a given experiment. However, expression of reference genes varies significantly from one set of experiment to the other. Thus, selection of reference genes depends on the experimental conditions. Sometimes the average expression of two or three reference genes is taken as standard. This review consolidated the details of about 120 genes attempted for normalization during comparative expression analysis in 16 different plants. Plant species included in this review are Arabidopsis thaliana, cotton (Gossypium hirsutum), tobacco (Nicotiana benthamiana and N. tabacum), soybean (Glycine max), rice (Oryza sativa), blueberry (Vaccinium corymbosum), tomato (Solanum lycopersicum), wheat (Triticum aestivum), potato (Solanum tuberosum), sugar cane (Saccharum sp.), carrot (Daucus carota), coffee (Coffea arabica), cucumber (Cucumis sativus), kiwi (Actinidia deliciosa) and grape (Vitis vinifera). The list includes model and cultivated crop plants from both monocot and dicot classes. We have categorized plant-wise the reference genes that have been used for expression analyses in any or all of the four different conditions such as biotic stress, abiotic stress, developmental stages and various organs and tissues, reported till date. This review serves as a guide during the reference gene hunt for gene expression analysis studies.

Horticultural, systems-engineering and economic evaluations of short-term plant storage techniques as a labor management tool for vegetable grafting nurseries

This transdisciplinary study has a three-fold systems approach in evaluating a horticultural technology: 1) horticultural evaluations, 2) economic and resource analyses, and 3) systems engineering analyses, using low temperature storage as an example technology. Vegetable grafting is a technique to produce value-added seedlings but requires labor intensive nursery operations. Low temperature storage of seedlings for a short period of time can reduce peak production, but has not been evaluated at the extent demonstrated in this paper. Seedlings of 22 genotypes of Cucurbitaceae (cucurbit family) and Solanaceae (nightshade family) were evaluated for storability under selected temperatures and photosynthetic photon flux. Storability of Cucurbitaceous seedlings varied between 2 to 4 weeks at 12°C and 13 μmol m^-2 s^-1. Solanaceous seedlings were generally storable for 4 weeks at 12°C and 13 μmol m^-2 s^-1, but tomato seedlings could be stored for 4 weeks at 10°C and 5 μmol m^-2 s^-1. Capital and weekly operational costs of a low temperature storage system with a design that meets environmental requirements were estimated as $671 to $708 per m² footprint and $0.79 to $2.21 per m² footprint per week, respectively. Electricity costs per plant was less than 0.1 cents for 2 to 4 weeks of storage. Using a schedule-optimization heuristic and a logistics simulator previously developed for grafting nursery operations, six production scenarios consisting of two crops (tomato or watermelon) and three production peak patterns were examined to evaluate the impact of including low temperature storage. While the overall average costs of grafting labor were not significantly different, maximum labor demand and grafting labor cost during the peak production week were reduced by 31% to 50% and 14% to 30% by using storage, respectively. Therefore, low temperature storage can be an effective means to address the issue of labor management in grafting nurseries.

Isolation of a novel alginate lyase-producing Bacillus litoralis strain and its potential to ferment Sargassum horneri for biofertilizer

Algae have long been used to augment plant productivity through their beneficial effects. Alginate oligosaccharide is believed to be one of the important components to enhance growth and crop yield. In this study, we isolated and characterized a Bacillus litoralis strain, named Bacillus M3, from decayed kelps. We further demonstrated that the M3 strain could secrete alginate lyase to degrade alginate. The crude enzyme exhibited the highest activity (33.74 U/mg) at pH 7.0 and 50°C. The M3 strain was also able to ferment the brown alga Sargassum horneri. Fermentation results revealed that a fermentation period of 8-12 hr was the best harvest time with the highest level of alginate oligosaccharides. Plant growth assay showed that the seaweed fermentation extract had an obvious promotion effect on root and seedling growth of Lycopersicon eseulentum L. Our results suggest that fermentation extract of Sargassum horneri by the novel strain of Bacillus litoralis M3 has significant development potential for biofertilizer production and agriculture application.

Androgenesis in Solanaceae

The Solanaceae is one of the most important families for global agriculture. Among the different solanaceous species, tobacco (Nicotiana tabacum), potato (Solanum tuberosum), tomato (Solanum lycopersicum), eggplant (Solanum melongena), and pepper (Capsicum annuum) are five crops of outstanding importance worldwide. In these crops, maximum yields are produced by hybrid plants created by crossing pure (homozygous) lines with the desired traits. Pure lines may be produced by conventional breeding methods, which is time consuming and costly. Alternatively, it is possible to accelerate the production of pure lines by creating doubled haploid (DH) plants derived from (haploid) male gametophytes or their precursors (androgenesis). In this way, the different steps for the production of pure lines can be reduced to only one generation, which implies important time and cost savings. This and other advantages make androgenic DHs the choice in a number of important crops where any of the different experimental in vitro techniques (anther culture or isolated microspore culture) is well set up. The Solanaceae family is an excellent example of heterogeneity in terms of response to these techniques, including highly responding species such as tobacco, considered a model system, and tomato, one of the most recalcitrant species, where no reliable and reproducible methods are yet available. Interestingly, the first evidence of androgenesis, particularly through in vitro anther culture, was demonstrated in a solanaceous species, Datura innoxia. In this chapter, we report the state of the art of the research about androgenic DHs in Solanaceae, paying special attention to datura, tobacco, potato, tomato, eggplant, and pepper.

Widespread flower color convergence in Solanaceae via alternate biochemical pathways

Phenotypic convergence is rampant throughout the tree of life. While recent studies have made significant progress in ascertaining the proximate mechanisms underlying convergent phenotypes, less is known about the frequency and predictability with which convergent phenotypes arise via the same or multiple pathways at the macroevolutionary scale. We investigated the proximate causes and evolutionary patterns of red flower color in the tomato family, Solanaceae, using large-scale data mining and new sequence data to reconstruct a megaphylogeny of 1341 species. We then combined spectral and anatomical data to assess how many times red flowers have evolved, the relative contribution of different pathways to independent origins of red, and whether the underlying pathway is predicted by phylogenetic relatedness. We estimated at least 30 relatively recent origins of red flowers using anthocyanins, carotenoids, or a dual production of both pigments, with significant phylogenetic signal in the use of anthocyanins and dual production, indicating that closely related red-flowered species tend to employ the same mechanism for coloration. Our study is the first to test whether developmental pathways exhibit phylogenetic signal and implies that historical contingency strongly influences the evolution of new phenotypes.

Meristem maturation and inflorescence architecture--lessons from the Solanaceae

Plant apical meristems (AMs) grow continuously by delicately balancing cells leaving at the periphery to form lateral organs with slowly dividing central domain cells that replenish reservoirs of pluripotent cells. This balance can be modified by signals originating from within and outside the meristem, and their integration results in a gradual maturation process that often culminates with the meristem differentiating into a flower. Accompanying this 'meristem maturation' are changes in spacing and size of lateral organs and in rates at which lateral meristems are released from apical dominance. Modulation of distinct meristem maturation parameters through environmental and genetic changes underlies the remarkable diversity of shoot architectures. Here, we discuss recent studies relating the dynamics of meristem maturation with organization of floral branching systems--inflorescences--in the nightshades. From this context, we suggest general principles on how factors coordinating meristem maturation impact shoot organization more broadly.

Tricolorin A as a natural herbicide

Tricolorin A acts as pre- and post-emergence plant growth inhibitor. In pre-emergence it displays broad-spectrum weed control, inhibiting germination of both monocotyledonous (Lolium mutliflorum and Triticum vulgare) and dicotyledonous (Physalis ixocarpa and Trifolium alexandrinum) seeds, being the dicotyledonous seeds the most inhibited. Tricolorin A also inhibited seedling growth, and seed respiration, and since the concentrations required for inhibiting both germination and respiration were similar, we suggest that respiration is one of its targets. Tricolorin A at 60 µM acts as a post- emergence plant growth inhibitor by reducing dry plant biomass by 62%, 37%, 33%, and 22% for L. multiflorum, T. alexandrinum, T. vulgare, and P. ixocarpa, respectively, 18 days after its application. In order to determine the potency of tricolorin A as a plant growth inhibitor, paraquat was used as control; the results indicate that tricolorin A acts as a non-selective post-emergence plant growth inhibitor similar to paraquat, since both reduced the biomass production in P. ixocarpa and T. alexandrinum. Therefore, we suggest that tricolorin A will be a good biodegradable herbicide for weeds.

Divergences of MPF2-like MADS-domain proteins have an association with the evolution of the inflated calyx syndrome within Solanaceae

The inflated calyx syndrome (ICS) is a post-floral novelty within Solanaceae. Previous work has shown that MPF2-like MADS-box genes have been recruited for the development and evolution of ICS through heterotopic expression from vegetative to floral organs. ICS seems to be a plesiomorphic trait in Physaleae, but it has been secondarily lost in some lineages during evolution. We hypothesized that molecular and functional divergences of MPF2-like proteins might play a role in the loss of ICS. In this study we analyzed the phylogeny, selection and various functions of MPF2-like proteins with respect to the evolution of ICS. Directional selection of MPF2-like orthologs toward evolution of ICS was detected. While auto-activation capacity between proteins varies in yeast, MPF2-like interaction with floral MADS-domain proteins is robustly detected, hence substantiating their integration into the floral developmental programs. Dimerization with A- (MPF3) and E-function (PFSEP1/3) proteins seems to be essential for ICS development within Solanaceae. Moreover, the occurrence of the enlarged sepals, reminiscent of ICS, and MPF2-like interactions with these specific partners were observed in transgenic Arabidopsis. The interaction spectrum relevant to ICS seems to be plesiomorphic, reinforcing the plesiomorphy of this trait. The inability of some MPF2-like to interact with either the A-function or any of the E-function partners characterized is correlated with the loss of ICS in the lineages that showed a MPF2-like expression in the calyx. Our findings suggest that, after recruitment of MPF2-like genes for floral development, diversification in their coding region due to directional selection leads to a modification of the MADS-domain protein interacting spectrum, which might serve as a constraint for the evolution of ICS within Solanaceae.

Sprout vacuum-infiltration: a simple and efficient agroinoculation method for virus-induced gene silencing in diverse solanaceous species

Virus-induced gene silencing (VIGS) is a robust technique for identifying the functions of plant genes. Tobacco rattle virus (TRV)-mediated VIGS has been commonly used in many plants. In order to overcome the limitations of existing agroinoculation methods, we report an easy and effective method of agroinoculation for virus-induced gene silencing-sprout vacuum-infiltration (SVI). Using sprout vacuum-infiltration, we have successfully silenced the expression of phytoene desaturase and Mg-protoporphyrin chelatase genes in four important solanaceous crops, including tomato, eggplant, pepper, and Nicotiana benthamiana. The gene-silenced phenotypes are conspicuous in 1-week-old plants. The method is simple, low cost and rapid compared to other techniques such as leaf infiltration or agrodrench. It may be more practical for studying gene function in the early stages of plant growth. An important aspect of SVI is that it will be used for high-throughput VIGS screens in the future. SVI will be an effective tool to overcome the limitations of current inoculation methods and to facilitate large-scale VIGS analysis of cDNA libraries.

KEY MESSAGE

SVI is a simple, low cost agroinoculation method for VIGS. It is practical for studying the function of genes expressed in early stages of plant growth and high-throughput VIGS screens.

Under cover of darkness, caterpillars take flight: the immature stages and feeding ecology of the glasswinged butterfly, Oleria baizana in eastern Ecuador

This paper describes the morphology and behavior of the immature stages of Oleria baizana (Haensch) (Lepidoptera: Nymphalidae) from northeastern Ecuador. Brugmansia aurea Lagerh. (Solanales: Solanaceae) is the larval food plant. Eggs are laid singly, off of the host plant in the leaf litter. During the night, larvae climb a food plant seedling and sever a leaf petiole, parachuting with the leaf to the ground where they remain while feeding. Oleria baizana has five larval stadia, and individuals take 77 days to mature from oviposition to adult stage.

Comparative anatomical and developmental analysis of dry and fleshy fruits of Solanaceae

PREMISE OF THE STUDY

An anatomical examination of dry and fleshy fruits within the Solanaceae was carried out to identify comparable stages throughout development as well as features exclusive to each type of fruit. We studied fruit development of Nicotiana and Petunia, which have the plesiomorphic capsular fruit; Solanum and Iochroma, characterized by a derived fleshy berry; Cestrum, an independent origin of a fleshy fruit; and Datura, a reversion to a dry fruit. •

METHODS

Pre- and postanthesis carpels and fruits of all species were collected, sectioned, stained, and examined using light microscopy. •

KEY RESULTS

Comparable stages of carpel and fruit development were identified in all species. Furthermore, anatomical and developmental features were identified that characterize capsules in Solanaceae, including lack of increase in the number of pericarp cell layers, formation of a sclerified endocarp, and elongation of the epidermal cells of the placenta. Pericarps of fleshy fruits of the Solanoideae are characterized by abundant collenchyma, an increase in the number of cell layers, and a parenchymatous endocarp often expanding into the locules. Anatomical data show that early developmental stages of the fruit of Cestrum, a berry, are similar to the capsular fruits of Petunia and Nicotiana; similarly, Datura, one of the few capsular members of the Solanoideae, shares several anatomical features with closely related berried taxa. •

CONCLUSIONS

Ontogenetically, all fleshy or all dry fruits do not necessarily share a common developmental ground plan. Independent evolution of fleshiness, sclerification, dryness, and dehiscence are discussed in a phylogenetic context.

Robustness and evolvability in the B-system of flower development

BACKGROUND

Gene duplication has often been invoked as a key mechanism responsible for evolution of new morphologies. The floral homeotic B-group gene family has undergone a number of gene duplication events, and yet the functions of these genes appear to be largely conserved. However, detailed comparative analysis has indicated that such duplicate genes have considerable cryptic variability in their functions. In the Solanaceae, two duplicate B-group gene lineages have been retained in three subfamilies. Comparisons of orthologous genes across members of the Solanaceae have demonstrated that the combined function of all four B-gene members is to establish petal and stamen identity, but that this function was partitioned differently in each species. These observations emphasize both the robustness and the evolvability of the B-system.

SCOPE

We provide an overview of how the B-function genes can robustly specify petal and stamen identity and at the same time evolve through changes in protein-protein interaction, gene expression patterns, copy number variation or alterations in the downstream genes they control. By using mathematical models we explore regulatory differences between species and how these impose constraints on downstream gene regulation.

CONCLUSIONS

Evolvability of the B-genes can be understood through the multiple ways in which the B-system can be robust. Quantitative approaches should allow for the incorporation of more biological realism in the representations of these regulatory systems and this should contribute to understanding the constraints under which different B-systems can function and evolve. This, in turn, can provide a better understanding of the ways in which B-genes have contributed to flower diversity.

Grafting as a research tool

Grafting as a means to connect different plant tissues has been enormously useful in many studies of long-distance signalling and transport in relation to regulation of development and physiology. There is an almost infinite number of pairwise graft combinations that can be tested, typically between two different genotypes and/or between plants previously exposed to different environmental treatments. Grafting experiments are especially powerful for unambiguous demonstration of spatial separation of source and target, including genetic complementation of mutant phenotypes across a graft union, direct detection of transmitted molecules in receiving tissue or vascular sap, and activation or suppression of molecular targets due to signal transmission. Although grafting has a long history in research, only in the past decade has it been applied extensively to the Arabidopsis model. This chapter compares the main Arabidopsis grafting methods now available and describes seedling grafting in detail. Information is also provided on grafting of other common research model species, together with outlines of some successful applications.

Weed management in Solanaceae crops in Portugal

Portugal has very good climatic-edafic conditions for Solanaceae crops, regarding to either yield quality or quantity. Tomato (Lycopersicon esculentum Miller.), potato (Solanum tuberosum L.) and pepper (Capsicum annuum L.) are the most social-economically important Solanaceae and aubergine (Solanum melongena L.) area of cultivation is increasing. Tomato is cultivated for fresh consumption and, primarily, for industrial processing. Is one of the most profitable vegetable crop and the main vegetable for industry. Potato is the annual vegetable crop with the largest cultivated area. Pepper is one of the main crops for vegetable frozen industry. Tomato, pepper and aubergine are cultivated in the field (outdoor) in Spring-Summer season. In greenhouses, they're also grown during other months and, at the southmost region (Algarve), during the whole year. Potato is cultivated almost the whole year through. Weed management is essential to achieve yield rentability and, for crops growing in the field, herbicides play an important role, due to their efficacy or inherent limitations of other control measures. This paper presents the state of art, in Portugal, regarding to some cultural and social-economical aspects of these crops (e.g., cultivated areas, productions, main producer regions), main weeds, weed control methods and, in particular, registered herbicides, with indication of their usage conditions (application timings and spectrum of weeds controlled) according to the principles of Good Plant Protection Practice and Integrated Weed Management.

Increase in respiratory cost at high growth temperature is attributed to high protein turnover cost in Petunia x hybrida petals

It is widely believed that turnover of nitrogenous (N) compounds (especially proteins) incurs a high respiratory cost. Thus, if protein turnover costs change with temperature, this would influence the dependence of respiration rate on growth temperature. Here, we examined the extent to which protein turnover cost explained differences in N-utilization costs (nitrate uptake/reduction, ammonium assimilation, amino acid and protein syntheses, protein turnover and amino acid export) and in respiration rate with changes in growth temperature. By measurements and literature data, we evaluated each N-utilization cost in Petunia x hybrida petals grown at 20, 25 or 35 degrees C throughout their whole lifespans. Protein turnover cost accounted for 73% of the integrated N-utilization cost on a whole-petal basis at 35 degrees C. The difference in this cost on a dry weight basis between 25 and 35 degrees C accounted for 75% of the difference in N-utilization cost and 45% of the difference in respiratory cost. The cost of nitrate uptake/reduction was high at low growth temperatures. We concluded that respiratory cost in petals was strongly influenced by protein turnover and nitrate uptake/reduction, and on the shoot basis, C investment in biomass was highest at 25 degrees C.

How polyamine synthesis inhibitors and cinnamic acid affect tropane alkaloid production

Hairy roots of Brugmansia candida produce the tropane alkaloids scopolamine and hyoscyamine. In an attempt to divert the carbon flux from competing pathways and thus enhance productivity, the polyamine biosynthesis inhibitors cyclohexylamine (CHA) and methylglyoxal-bis-guanylhydrazone (MGBG) and the phenylalanine-ammonia-lyase inhibitor cinnamic acid were used. CHA decreased the specific productivity of both alkaloids but increased significantly the release of scopolamine (approx 500%) when it was added in the mid-exponential phase. However, when CHA was added for only 48 h during the exponential phase, the specific productivity of both alkaloids increased (approx 200%), favoring scopolamine. Treatment with MGBG was detrimental to growth but promoted release into the medium of both alkaloids. However, when it was added for 48 h during the exponential phase, MGBG increased the specific productivity (approx 200%) and release (250- 1800%) of both alkaloids. Cinnamic acid alone also favored release but not specific productivity. When a combination of CHA or MGBG with cinnamic acid was used, the results obtained were approximately the same as with each polyamine biosynthesis inhibitor alone, although to a lesser extent. Regarding root morphology, CHA inhibited growth of primary roots and ramification. However, it had a positive effect on elongation of lateral roots.

Conservation and divergence of both phosphate- and mycorrhiza-regulated physiological responses and expression patterns of phosphate transporters in solanaceous species

Here, orthologous genes of six phosphate transporter (PiT) genes, which are members of the Pht1 and Pht2 families in tomato and potato, have been cloned from the solanaceous species pepper, eggplant and tobacco. Overall, expressions of these genes in pepper, eggplant and tobacco showed similar patterns to those in tomato and potato: P-starvation enhancement in both leaves and roots for Pht1;1, P-depletion induction exclusively in roots for Pht1;2, mycorrhizal enhancement for Pht1;3, and mycorrhizal induction for both Pht1;4 and Pht1;5. In the roots of nonmycorrhizal eggplant, SmPht1;3, SmPht1;4 and SmPht1;5 were also expressed under extreme P starvation. Mycorrhizal symbiosis under high-P supply conditions reduced plant growth, with concurrent enhancement of Pht1;2 expression in the roots of pepper as well as eggplant. In addition, the mycorrhizal symbiosis down-regulated the expression of Pht2;1 genes greatly in the leaves of pepper and tobacco. The discrepancies between the evolutionary distances of the PiT genes and their expression patterns among the five species suggest greater complexity in function of PiT in plants than previously expected.

Trichomes: different regulatory networks lead to convergent structures

Sometimes, proteins, biological structures or even organisms have similar functions and appearances but have evolved through widely divergent pathways. There is experimental evidence to suggest that different developmental pathways have converged to produce similar outgrowths of the aerial plant epidermis, referred to as trichomes. The emerging picture suggests that trichomes in Arabidopsis thaliana and, perhaps, in cotton develop through a transcriptional regulatory network that differs from those regulating trichome formation in Antirrhinum and Solanaceous species. Several lines of evidence suggest that the duplication of a gene controlling anthocyanin production and subsequent divergence might be the major force driving trichome formation in Arabidopsis, whereas the multicellular trichomes of Antirrhinum and Solanaceous species appear to have a different regulatory origin.

In vitro shoot and root organogenesis, plant regeneration and production of tropane alkaloids in some species of Schizanthus

A rapid in vitro propagation system leading to formation of shoots from callus, roots, and plantlets was developed for Schizanthus hookeri Gill. (Solanaceae), an endemic Chilean plant. The genus Schizanthus is of particular interest due to the presence of several tropane alkaloids. So far, in vitro propagation of species of this genus has not been reported. Propagation of S. hookeri consisted of two phases, the first one for callus initiation and shoot formation and the second for rhizogenesis and plantlet regeneration. From a single callus that rapidly increased in cell biomass (from approximately 50 mg to approximately 460 mg/culture tube [25 x 130 mm] in 60 days) in the presence of 2.69 microM NAA and 2.22 microM BA, more than 10 shoots/callus explant were formed. From the latter, approx. twenty plantlets formed after 90-110 days shoot subculture in medium devoid of growth regulators that favored root formation. Ten alkaloids ranging from simple pyrrolidine derivatives to tropane esters derived from angelic, tiglic, senecioic or methylmesaconic acids were obtained from in vitro regenerated plantlets. One of them, 3alpha-methylmesaconyloxytropane, was not previously described. The same growth conditions, as well as other growth regulator levels tested, were required to induce callus and root formation in S. grahamii Gill. Root organogenesis occurred despite a high level of BA vs. NAA used, (i.e., 4.44 microM BA and 0.54 microM NAA); however no shoot formation was achieved. In the case of S. tricolor Grau et Gronbach, only callus formation was obtained in the presence of various growth regulators.

From phenotypic to molecular polymorphisms involved in naturally occurring variation of plant development

An enormous amount of naturally occurring genetic variation affecting development is found within wild and domesticated plant species. This diversity is presumably involved in plant adaptation to different natural environments or in human preferences. In addition, such intraspecific variation provides the basis for the evolution of plant development at larger evolutionary scales. Natural phenotypic differences are now amenable to genetic dissection up to the identification of causal DNA polymorphisms. Here we describe 30 genes and their functional nucleotide polymorphisms currently found as underlying allelic variation accounting for plant intraspecific developmental diversity. These studies provide molecular and cellular mechanisms that determine natural variation for quantitative and qualitative traits such as: fruit and seed morphology, colour and composition; flowering time; seedling emergence; plant architecture and inflorescence or flower morphology. Besides, analyses of flowering time variation within several distant species allow molecular comparisons between species, which are detecting homologous genes with partly different functions and unrelated genes with analogous functions. Thus, considerable gene function differences are being revealed also among species. Inspection of a catalogue of intraspecific nucleotide functional polymorphisms shows that transcriptional regulators are the main class of genes involved. Furthermore, barely more than half of the polymorphisms described are located in coding regions and affect protein structure, while the rest are regulatory changes altering gene expression. These limited analyses of intraspecific developmental variation support Doebley and Lukens's proposition (1998) that modifications in cis -regulatory regions of transcriptional regulators represent a predominant mode for the evolution of novel forms, but await more detailed studies in wild plant species.

Induced defense in Nicotiana attenuata (Solanaceae) fruit and flowers

Plants protect themselves against herbivory using a continuum of strategies, ranging from constitutive defenses to intermittent induced responses. Induced defenses may not provide immediate and maximum protection, but could be advantageous when continuous defense is either energetically or ecologically costly. As such, induced defenses in flowers could help defend relatively valuable tissue while keeping reproductive structures accessible and attractive to pollinators. Thus far, no one has demonstrated the efficacy of induced defenses against floral herbivores (florivores) in the field. Here we show that mechanical leaf damage in wild tobacco, Nicotiana attenuata (Solanaceae), reduced both flower and fruit herbivory in the field and that exogenous application of methyl jasmonate, a potent elicitor of induced responses, reduced both leaf and floral damage in natural populations. This result is consistent with a survey of damage in the field, which showed a negative relationship between leaf damage and flower and fruit damage. Although optimal defense theory predicts that induced defenses should be rare in reproductive tissues, owing to their high fitness value, our results suggest otherwise. Induced defenses in leaves and reproductive tissues may allow plants to respond effectively to the concomitant pressures of defending against herbivory and attracting pollinators.

Control strategies for sweet potato virus disease in Africa

Sweet potato virus disease (SPVD), caused by dual infection with the whitefly-borne Sweet potato chlorotic stunt virus (SPCSV) and the aphid-borne Sweet potato feathery mottle virus (SPFMV), is the most serious disease of sweet potato in Africa. SPVD has been known there since at least the 1940s, although it took several decades to elucidate its aetiology. It occurs throughout Africa and is particularly prevalent in the Great Lakes region. Production of sweet potato is largely by resource-poor farmers, growing mostly local landraces and for home consumption and so control strategies need to be appropriate to these circumstances. Most high yielding and/or early maturing landraces in Uganda are susceptible to SPVD and most resistant landraces are low-yielding, forcing farmers to compromise between the conflicting requirements of large and/or early yields, and food security. Accordingly, two strategies were tested to avoid the disadvantages associated with such compromises. These were deploying high-yielding SPVD-resistant cultivars and phytosanitation practices to enable susceptible landraces to be grown successfully. In on-farm trials in Masaka and Rakai Districts of Uganda, some SPVD-resistant cultivars bred at Namulonge Agricultural and Animal Research Station (NAARI), in Wakiso District, out-yielded local landraces. Other trials at NAARI and at nearby farms showed that roguing diseased cuttings within 1 month of planting and isolation from diseased crops, even by as little as 15m, can considerably decrease spread of SPVD to susceptible cultivars. This indicates that phytosanitation can protect desirable susceptible cultivars, even if adopted only locally. A dual approach of deploying both resistant varieties and phytosanitation provides farmers with a valuable increase in their choice of control strategies for SPVD.

A dwarf mutant strain of Pharbitis nil, Uzukobito (kobito), has defective brassinosteroid biosynthesis

Japanese morning glory (Pharbitis nil) is a model plant characterized by a large stock of spontaneous mutants. The recessive mutant Uzukobito shows strong dwarfism with dark-green rugose leaves. The phenotype was rescued by the application of brassinolide, a bioactive brassinosteroid (BR), indicating that Uzukobito was a BR-deficient mutant. A detailed analysis of the endogenous BR levels in Uzukobito and its parental wild-type plant showed that Uzukobito had a lower level of BRs downstream of (24R)-24-methyl-5alpha-cholestan-3-one and (22S, 24R)-22-hydroxy-24-methyl-5alpha-cholestan-3-one than those in wild-type plants, while their immediate precursors (24R)-24-methylcholest-4-en-3-one and (22S, 24R)-22-hydroxy-24-methylcholest-4-en-3-one accumulated relatively more in Uzukobito. These results indicate that Uzukobito had a defect in the conversion of (24R)-24-methylcholest-4-en-3-one and (22S, 24R)-22-hydroxy-24-methylcholest-4-en-3-one to their 5alpha-reduced forms, which is catalyzed by de-etiolated2 (DET2) in Arabidopsis. The P. nil ortholog of the DET2 gene (PnDET2) was cloned and shown to have the greatest similarity to DET2 among all the putative genes in Arabidopsis. Uzukobito had one amino acid substitution from Glu62 to Val62 in the deduced amino acid sequence of PnDET2. Recombinant PnDET2 expressed in COS-7 cells was found to be a functional steroid 5alpha-reductase (S5alphaR) converting (24R)-24-methylcholest-4-en-3-one to (24R)-24-methyl-5alpha-cholestan-3-one, while PnDET2 with the mutation did not show any catalytic activity. This shows that a plant S5alphaR can convert an intrinsic substrate. All these results clearly demonstrate that the Uzukobito phenotype resulted from a mutation on PnDET2, and a morphological mutant has been characterized at the molecular level among a large stock of P. nil mutants.

Tropane alkaloids in adventitious root cultures of Physochlaina physaloides

Adventitious root cultures of Physochlaina physaloides were established and their growth and tropane alkaloid production were investigated. Although the roots cultured in Murashige-skoog liquid medium containing 1.0-3.0 mg/l IBA grew well, the addition of lower concentrations of auxins was more suitable for alkaloid production. The best alkaloid yield was obtained with 0.01 mg/l NAA in 1/2 MS liquid medium. In addition, the alkaloid differences between the cultured roots and the regenerated plant cultivated in the soil was studied. Cultured roots in this condition showed higher level of alkaloids when compared to leaf, stem and roots from the regenerated plant (3 months in field conditions).

Tropane alkaloids in auxin-independent root cultures of Physochlaina physaloides

Adventitious and hairy root cultures of Physochlaina physaloides were established. These roots grew well and produced high amounts of tropane alkaloids (particularly hyoscyamine and 6 beta-hydroxyhyoscyamine) in auxin-free culture medium. The effects of basal media and temperature on the growth and alkaloid production of these roots were investigated. Both root cultures produced highest amount of tropane alkaloids in B5 medium though the optimum temperature for hairy roots were lower than that for adventitious roots.

Anther wall formation in Solanaceae species

Anther wall formation was studied in 32 species belonging to 27 genera of Solanaceae. Dicotyledonous and basic types of wall formation were observed, as well as several deviations due to subsequent periclinal divisions in the layers formed (middle layers and sometimes the endothecium). One type of wall formation was observed in each species. Some genera are uniform in their type of wall formation, while others are heterogeneous; a similar situation was observed at the tribal level. Summarizing all reported information on anther wall formation in the Solanaceae, 64 % of species show the basic type, while the remaining 36 % show the dicotyledonous type. Thus, neither type predominates, and no single type characterizes genera, tribes or the entire family.

Recent advances in fruit development and ripening: an overview

This article provides an overview of the Journal of Experimental Botany Special Issue on Fruit Development and Ripening. It reports that significant progress is being made in identifying genes controlling the development of dry dehiscent fruits in the model plant species Arabidopsis thaliana. In plants with fleshy fruits, a major focus has been the dissection of biochemical and genetic regulatory cascades controlling ripening, using tomato as a model species. Intermediates of the ethylene-signalling cascade, potential cross-talk between ethylene and auxin signals, and the role of ethylene-independent signals have all been described in this climacteric fruit. The recent isolation of the NOR and LeMADS-RIN genes, which participate in ethylene-independent signalling in tomato, and the discovery that a homologue of the RIN gene is expressed in strawberry, a non-climacteric fruit, suggests that common regulatory cascades may operate in all fruits. Transcriptional profiling during the development and ripening of both climacteric (tomato) and non-climacteric (strawberry) fruit has supported these observations, and also identified a number of novel genes involved in the biochemistry of fruit development and ripening. The use of phylogenies based on chloroplast gene sequences has allowed an insight into the evolution of fruit forms and fruit biochemistry, which may be useful for the manipulation of commercial species. Several molecular approaches, including positional cloning, QTL mapping and genetic engineering, are helping to define the biochemical and molecular bases of texture, flavour, colour, and aroma. As the understanding of the biology of fruit ripening has improved, so has the ability to improve the organoleptic and nutritional qualities of fruits through crop management, breeding or biotechnology.

Tobacco to tomatoes: a phylogenetic perspective on fruit diversity in the Solanaceae

The Solanaceae contains many species of agricultural importance. Several of these are cultivated for their fruits, such as the tomato, the pepper and the aubergine. The family is very diverse in fruit type with capsules, drupes, pyrenes, berries, and several sorts of dehiscent non-capsular fruits occurring in the 90+ genera. In this paper, recent work on fruit type evolution in angiosperms is reviewed in relation to dispersal agents and habitat ecology. Defining fruit types in the Solanaceae in a simple five state system, then mapping them onto a previously published molecular phylogeny based on chloroplast DNA allows discussion of the evolution of these fruit types in a phylogenetic framework. Capsules are plesiomorphic in the family, and although berries are a synapomorphy (shared derived character) for a large clade including the genus Solanum (tomatoes and aubergines), they have arisen several times in the family as a whole. Problems with homology of drupes and pyrenes are discussed, and areas for future investigation of fruit structure homology identified. The distribution of fruit types in the large and diverse genus Solanum is also discussed in the light of monophyletic groups identified using chloroplast gene sequences. This variety is related to recent advances in the understanding of the molecular biology of fruit development. Finally, several key areas of future comparative, phylogenetic investigation into fruit type evolution in the family are highlighted.

Shoot meristem maintenance is controlled by a GRAS-gene mediated signal from differentiating cells

Plant shoot development depends on the perpetuation of a group of undifferentiated cells in the shoot apical meristem (SAM). In the Petunia mutant hairy meristem (ham), shoot meristems differentiate postembryonically as continuations of the subtending stem. HAM encodes a putative transcription factor of the GRAS family, which acts non-cell-autonomously from L3-derived tissue of lateral organ primordia and stem provasculature. HAM acts in parallel with TERMINATOR (PhWUSCHEL) and is required for continued cellular response to TERMINATOR and SHOOTMERISTEMLESS (PhSTM). This reveals a novel mechanism by which signals from differentiating tissues extrinsically control stem cell fate in the shoot apex.

Successive glycosyltransfer activity and enzymatic characterization of pectic polygalacturonate 4-alpha-galacturonosyltransferase solubilized from pollen tubes of Petunia axillaris using pyridylaminated oligogalacturonates as substrates

Polygalacturonate 4-alpha-galacturonosyltransferase (pectin synthase) was solubilized from pollen tubes of Petunia axillaris and characterized. To accomplish this, an assay method using fluorogenic pyridylaminated-oligogalacturonic acids (PA-OGAs) as acceptor substrates was developed. When the pollen tube enzyme was solubilized with 0.5% (v/v) Triton X-100 and was incubated with PA-OGA and UDP-galacturonic acid (UDP-GalUA), successive transfer activity of more than 10 GalUAs from UDP-GalUA to the nonreducing end of PA-OGA was observed by diethylaminoethyl high-performance liquid chromatography. This activity was time- and enzyme concentration-dependent. The optimum enzyme activity was observed at pH 7.0 and 30 degrees C. Among the PA-OGAs investigated, those with a degree of polymerization of more than 10 were preferred as substrates. The crude pollen tube enzyme had an apparent K(m) value of 13 microM for the PA-OGA with a degree of polymerization 11 and 170 microM for UDP-GalUA. The characteristics of the P. axillaris pollen tube enzyme and the usefulness of fluorogenic PA-OGAs for the assay of this enzyme are discussed.

Structural and ultrastructural analysis of Solanum lycopersicoides protoplasts during diploid plant regeneration

Light, fluorescence and electron microscopy were used to analyse the structural properties of protoplasts obtained from established suspension culture of Solanum lycopersicoides Dun, composed of meristematic cell aggregates. Four types of protoplasts were distinguished immediately after isolation: (1) mononuclear; (2) polynuclear, (3) anuclear and (4) homogeneous protoplasts. Only mononuclear protoplasts were capable of complete cell wall regeneration and mitotic division. Other types of protoplasts were eliminated during culture. Three phases were distinguished in the developing protoplast culture: (1) the elimination phase during which protoplasts damaged during isolation underwent complete degradation; (2) a phase of intense division during which both mitotic cell division and amitotic nuclear division took place; and (3) a stabilization phase leading to the formation of suspension culture. The cell suspension culture obtained from protoplasts was capable of regenerating diploid plants.

Microorganisms asssociated with Withania somnifera leaves

Microorganisms including bacteria, actinomycetes and fungi were recovered from the leaves of Withania somnifera, which were collected from two altitudinal ranges (0-300 m and 1700-2000 m) in the Asir region, Saudi Arabia. Types and numbers of microorganisms varied according to the altitude and the month of collection. The number of microorganisms was higher on old leaves than that on young ones in most cases. Low altitude exhibited more microorganisms than high altitude. The relationship between meteorological factors and type and number of the recovered microorganisms is discussed. Inoculation of detached healthy leaves of Withania by all recovered fungal species revealed only Alternaria solani as a pathogen of this plant. To confirm pathogenicity, scanning and transmission electron microscopic examination revealed the colonization of this pathogen inside the leaf tissue. Penetration of Withania leaves by the fungus occurred only through stomata, and the invading hyphae were located in the intercellular spaces of leaf tissues. Ultrastructural changes noted in infected cells included changes in chloroplasts and the invagination of the host plasma membrane.

Effect of elicitation on growth, respiration, and nutrient uptake of root and cell suspension cultures of Hyoscyamus muticus

The elicitation of Hyoscyamus muticus root and cell suspension cultures by fungal elicitor from Rhizoctonia solani causes dramatic changes in respiration, nutrient yields, and growth. Cells and mature root tissues have similar specific oxygen uptake rates (SOUR) before and after the onset of the elicitation process. Cell suspension SOUR were 11 and 18 micromol O2/g FW x h for non-elicited control and elicited cultures, respectively. Mature root SOUR were 11 and 24 micromol O2/g FW x h for control and elicited tissue, respectively. Tissue growth is significantly reduced upon the addition of elicitor to these cultures. Inorganic yield remains fairly constant, whereas yield on sugar is reduced from 0.532 to 0.352 g dry biomass per g sugar for roots and 0.614 to 0.440 g dry biomass per g sugar for cells. This reduction in yield results from increased energy requirements for the defense response. Growth reduction is reflected in a reduction in root meristem (tip) SOUR, which decreased from 189 to 70 micromol O2/g FW x h upon elicitation. Therefore, despite the increase in total respiration, the maximum local oxygen fluxes are reduced as a result of the reduction in metabolic activity at the meristem. This distribution of oxygen uptake throughout the mature tissue could reduce mass transfer requirements during elicited production. However, this was not found to be the case for sesquiterpene elicitation, where production of lubimin and solavetivone were found to increase linearly up to oxygen partial pressures of 40% O2 in air. SOUR is shown to similarly increase in both bubble column and tubular reactors despite severe mass transfer limitations, suggesting the possibility of metabolically induced increases in tissue convective transport during elicitation.

Ethylene response to pollen tube growth in Nicotiana tabacum flowers

In flowers of Nicotiana tabacum L., pollination induces a transient increase in ethylene production by the pistil. The characteristic dynamics of the increase in ethylene correspond to the main steps of the pollen-tube journey into the pistil: penetration into the stigma, growth through the style, entry into the ovary and fertilization. Ethylene is synthesized de novo in the pistil, and its production is reduced in the dark. Ethylene production was monitored in tobacco flowers after pollination with incongruous pollen from three different Nicotiana species, N. rustica, N. repanda and N. trigonophylla, and with pollen from Petunia hybrida. Pollen from all of these different sources can germinate on the stigma surface but each pollen type shows a different behavior and efficiency in penetrating the pistil tissues. Thus, these different crosses provided a model with which to study the response of the pistil to pollination and fertilization. Ethylene evolution upon pollination in tobacco differed in each cross, suggesting that ethylene is correlated with the response to pollen tube growth in the tobacco flower.

Cloning and characterization of a thermal hysteresis (antifreeze) protein with DNA-binding activity from winter bittersweet nightshade, Solanum dulcamara

The gene for a thermal hysteresis (antifreeze) protein (sthp-64) from the bittersweet nightshade, Solanum dulcamara, was cloned and characterized. An expression cDNA library prepared from November S. dulcamara was screened using a polyclonal antibody generated against a previously purified 67 kDa thermal hysteresis protein, and positive clones were identified and sequenced. The full-length thermal hysteresis protein gene was cloned into an Escherichia coli expression vector and expressed as a fusion protein. The putative thermal hysteresis protein (STHP-64) contains two conserved regions 56 and 57 amino acids in length which have the C-X4-C-X22-23-H-X1-H zinc finger motif which is present in WRKY proteins, a family of transcription factors which play a role in regulating expression of pathogenesis-related proteins in plants. Additional features of transcription factors, such as an acidic domain between the two zinc-fingers and a glutamine-rich region upstream of the first zinc-finger are also present in STHP-64. A DNA binding assay showed that the expressed STHP-64 fusion protein has specific DNA-binding ability. A unique feature of STHP-64 is that the C-terminus contains 10 consecutive 13-mer repeats. Such repeats are a common feature of animal antifreeze proteins. The expressed STHP-64 fusion protein had low levels of thermal hysteresis activity, but this activity was considerably increased by addition of citrate, which is known as an enhancer of certain insect antifreeze proteins. Northern blots demonstrated that the STHP-64 transcript was not present in leaves until November and December, suggesting that cold acclimation induces STHP-64 production.

Two flavonoid glucosyltransferases from Petunia hybrida: molecular cloning, biochemical properties and developmentally regulated expression

Two flavonoid glucosyltransferases, UDP-glucose:flavonoid 3-0-glucosyltransferase (3-GT) and UDP-glucose: anthocyanin 5-O-glucosyltransferase (5-GT), are responsible for the glucosylation of anthocyani(di)ns to produce stable molecules in the anthocyanin biosynthetic pathway. The cDNAs encoding 3-GT and 5-GT were isolated from Petunia hybrida by hybridization screening with heterologous probes. The cDNA clones of 3-GT, PGT8, and 5-GT, PH1, encode putative polypeptides of 448 and 468 amino acids, respectively. A phylogenetic tree based on amino acid sequences of the family of glycosyltransferases from various plants shows that PGT8 belongs to the 3-GT subfamily and PH1 belongs to the 5-GT subfamily. The function of isolated cDNAs was identified by the catalytic activities for 3-GT and 5-GT exhibited by the recombinant proteins produced in yeast. The recombinant PGT8 protein could convert not only anthocyanidins but also flavonols into the corresponding 3-O-glucosides. In contrast, the recombinant PH1 protein exhibited a strict substrate specificity towards anthocyanidin 3-acylrutinoside, comparing with other 5-GTs from Perilla frutescens and Verbena hybrida, which showed broad substrate specificities towards several anthocyanidin 3-glucosides. The mRNA expression of both 3-GT and 5-GT increased in the early developmental stages of P. hybrida flower, reaching the maximum at the stage before flower opening. Southern blotting analysis of genomic DNA indicates that both 3-GT and 5-GT genes exist in two copies in P. hybrida, respectively. The results are discussed in relation to the molecular evolution of flavonoid glycosyltransferases.

Conservation in divergent solanaceous species of the unique gene structure and enzyme activity of a gametophytically-expressed flavonol 3-O-galactosyltransferase

Flavonol 3-O-galactosyltransferase (F3GalTase) is a pollen-specific enzyme which glycosylates the flavonols required for germination in petunia. The highly restricted tissue-specific expression and substrate usage make F3GalTase unique among all other flavonoid glycosyltransferases (GTs) described to date, including the well characterized Bronze 1 (Bz1) gene of maize. RFLP mapping, DNA gel blot, and sequence analyses showed that the single copy F3galtase gene has a different genomic organization than Bz1. Within the promoter of F3galtase are potential regulatory motifs which may confer pollen-specific gene expression and activation by Myb and bHLH transcription factors. However, we provide evidence that F3galtase is not regulated by An4, which encodes a Myb factor known to regulate anthocyanin accumulation in petunia anthers. An unexpected feature of the F3galtase promoter was the presence of large blocks of chloroplast and mitochondrial DNA. Gel blot analyses of genomic DNA from the progenitors of Petunia hybrida, as well as from Nicotiana tabacum, indicated that migration of organellar DNA into the F3galtase gene was an ancient event that occurred prior to speciation of the Solanaceae. Together with enzyme assays and HPLC analyses of pollen extracts from tobacco, tomato, and potato, these results confirmed that the unique F3galtase gene structure, enzyme activity, and pollen-specific flavonol glucosylgalactosides are conserved throughout the Solanaceae.

The role of SPY and its TPR domain in the regulation of gibberellin action throughout the life cycle of Petunia hybrida plants

SPY acts as a negative regulator of gibberellin (GA) action in Arabidopsis, but its mode of action and regulation are still unknown. SPY over-expression in transgenic petunia plants affected various GA-regulated processes, including seed germination, shoot elongation, flower initiation, flower development and the expression of a GA-induced gene, GIP. A similar phenotype was obtained when wild-type petunia plants were treated with the GA-biosynthesis inhibitor, paclobutrazol. The N-terminus of SPY contains tetratricopeptide repeats (TPR). TPR motifs participate in protein-protein interactions, suggesting that SPY is part of a multiprotein complex. To test this hypothesis, we over-expressed the SPY's TPR region without the catalytic domain in transgenic petunia and generated a dominant-negative SPY mutant. The transgenic seeds were able to germinate on paclobutrazol, suggesting an enhanced GA signal. We cloned the petunia SPY homologue, PhSPY, and showed that its mRNA level is not affected by GA or ABA. The results of this study support the role of SPY as a negative regulator of GA action, suggest that the TPR domain is required for the interaction with other proteins to form an active complex and indicate that different plants use similar mechanisms to transduce the GA signal.

Effects of light intensity and air velocity on air temperature, water vapor pressure, and CO2 concentration inside a plant canopy under an artificial lighting condition

In order to characterize environmental variables inside a plant canopy under artificial lighting in the CELSS, we investigated the effects of light intensity and air velocity on air temperature, water vapor pressure, and CO2 concentration inside a plant canopy. Under a PPF of 500 micromoles m-2 s-1, air temperature was 2-3 degrees C higher, water vapor pressure was 0.6 kPa higher, and CO2 concentration was 25-35 micromoles mol-1 lower at heights ranging from 0 to 30 mm below the canopy than at a height 60 mm above the canopy. Increasing the PPF increased air temperature and water vapor pressure and decreased CO2 concentration inside the canopy. The air temperature was lower and the CO2 concentration was higher inside the canopy at an air velocity of 0.3 m s-1 than at an air velocity of 0.1 m s-1. The environmental variables inside the canopy under a high light intensity were characterized by higher air temperature, higher vapor pressure, and lower CO2 concentration than those outside the canopy.

Hairy roots of Brugmansia candida that grow without agitation: biotechnological implications

Hairy roots of Brugmansia candida that grew without agitation were obtained. Kinetics of growth and production of the tropane alkaloids scopolamine and hyoscyamine, with and without agitation, were studied. The exponential growth rate was higher in the roots that were exposed to shaking (0.13 d(-1)) than in the nonagitated ones (0.09 d(-1)). The specific production and the levels per flask of both alkaloids were enhanced without shaking. The use of these roots in large-scale productions could be economically advantageous. It remains to be seen if the data obtained in shake flasks can be extrapolated to large-scale bioreactors.

Decreased scopolamine yield in field-grown Duboisia plants regenerated from hairy roots

Hairy root cultures were obtained from hybrid clones of Duboisia myoporoides x D. leichhardtii following transformation by Agrobacterium rhizogenes strain A4. Shoots spontaneously regenerating from the hairy root cultures were rooted and transferred to soil. The plants displayed typical morphological alterations known as hairy root syndrome to varying degrees. PCR analysis confirmed that all transformed plants contained the rolA, rolB and rolC genes, irrespective of the degree of morphological alterations. A field test of the transformed regenerated plants revealed that those plants displaying the strongest hairy root syndrome symptoms had the highest content of the tropane alkaloid scopolamine. However, the overall scopolamine and hyoscyamine yield of all transformed plants was clearly reduced compared to untransformed control plants. These results demonstrate that the A. rhizogenes-transformed plants tested in this study do not provide a viable alternative to agricultural farming of hybrid clones of D. myoporoides x D. leichhardtii obtained by conventional breeding.

In vitro propagation of Withania somnifera and isolation of withanolides with immunosuppressive activity

Withania somnifera plantlets were produced in vitro from the shoot-tip of aseptically germinated seedlings. Culture conditions were optimized using different plant growth regulators which gave rise to 120 shoots from a single bud. The plantlets were then transferred to pots and maintained in greenhouse for 4 months. 90% of these in vitro propagated plantlets survived and showed normal growth. Leaves from these plants were used for isolation of the withanolides. Methanolic extract of leaves from plantlets growing in tissue culture and those transferred to the greenhouse were evaluated for immunomodulatory activity. While the extract from greenhouse samples showed potent immunosuppressive activity, those from tissue cultures samples did not show any activity. Fractionation and characterization of withanolides, using HPLC, NMR, MS methods revealed the presence of withaferin A in the greenhouse samples. Our results indicate that Withania species may require longer time and better differentiation and also natural environment for the production of withaferin A.

Plant-growth inhibitory activity of cedrelanolide from Cedrela salvadorensis

The effect of cedrelanolide, the most abundant limonoid isolated from Cedrela salvadorensis (Meliaceae), was assayed as a plant-growth inhibitory compound against monocotyledonous and dicotyledonous seeds. This compound inhibited germination, seed respiration, and seedling dry weights of some plant species (Lolium multiflorum, var. Hercules, Triticum vulgare, var. Salamanca, Physalis ixocarpa, and Trifolium alexandrinum). Our results indicate that cedrelanolide interferes with monocot preemergence properties, mainly energy metabolism of the seeds at the level of respiration. In addition, the compound inhibits photophosphorylation, H+ uptake, and noncyclic electron flow. This behavior might be responsible for its plant-growth inhibitory properties and its possible role as an allelopathic agent.

Xv4-vrxv4: a new gene-for-gene interaction identified between Xanthomonas campestris pv. vesicatoria race T3 and wild tomato relative Lycopersicon pennellii

Strains of tomato race 3 (T3) of Xanthomonas campestris pv. vesicatoria elicit a hypersensitive response (HR) in leaves of Lycopersicon pennellii LA716. Genetic segregation of the resistance exhibited ratios near 3:1 in F2 populations, which confirmed that a single dominant gene controlled the inheritance of this trait. With the aid of a collection of introgression lines, restriction fragment length polymorphism, and cleaved amplified polymorphic sequence markers, the resistance locus was located on chromosome 3 between TG599 and TG134. An avirulence gene named avrXv4 was also isolated by mobilizing a total of 600 clones from a genomic DNA library of the T3 strain 91-118 into the X. campestris pv. vesicatoria strain ME90, virulent on L. pennellii. One cosmid clone, pXcvT3-60 (29-kb insert), induced HR in resistant plants. The avirulent phenotype of pXcvT3-60 was confirmed by comparing growth rates in planta and electrolyte leakages among transconjugants carrying a mutated or intact clone with the wild-type T3 strain 91-118. A 1.9-kb DNA fragment contained within a 6.8-kb active subclone was sequenced and was determined to carry an open reading frame of 1,077 bp. The predicted AvrXv4 protein exhibits high similarity to members of an emerging new family of bacterial proteins from plant and mammalian pathogens comprising AvrRxv, AvrBsT, YopJ, YopP, AvrA, and YL40.