PROGRAM & SPEAKERS

Mondher Bouzayen (INRA, INP/ENSAT Toulouse, FR)

AUXIN SIGNALLING IS A CENTRAL TRIGGER OF FRUIT SET AND PARTHENOCARPY

The making of a fruit is a developmental process unique to plants that involves a complex network of interacting genes and signalling pathways. It involves three main stages: (i) fruit set, (ii) fruit enlargement, and (iii) fruit ripening corresponding to transition steps associated with major metabolic reorientations and structural changes. Hormones play a central role in these developmental shifts but other clues are also involved in triggering of these processes. Indeed, successful pollination of the flower triggers theonset of ovary development into fruit, the so-called fruit set. However, the signaling components that drive the flower-to-fruit transition are not fully understood. Even though the role of auxin and GA is now well documented. The present study addresses the specific role of Auxin Response Factors (ARFs) and Aux/IAA in mediating auxin action at the onset of ovary development into fruit.  We show that down-regulation of SlIAA9, a tomato member of the Aux/IAA gene family, leads to fruit set independently from pollination giving rise to parthenocarpy. On the other hand, reverse genetics approaches revealed that up-regulation of SlARF8 and down-regulation of Sly-miR167 also lead to pollination-independent fruit set and to the production of seedless fruit. Overall, the study uncovers a complete regulome module controlling the flower-to-fruit transition which involves SlARF8 as a central figure and SlIAA9 and Sly-miR167 as components of the same mechanism underlying the fruit set process. The outcome of the study provides important clues for designing new breeding strategies for improving fruit yield in harsh environmental conditions and for producing parthenocarpic fruit.

Miquel Angel Conesa (University Illes Balears, SP)

STUDIES OF THE RAMELLET TOMATO LANDRACES MAY REVEAL A BASIS FOR EXTENDING FRUIT SHELF-LIFE AND THE SIGNIFICANCE OF WATER AVAILABILITY DURING CULTIVATION

Current improvement in horticultural crops is focused on increasing productivity, perdurability and nutritional content. However, projected climate changes will impose limitations with regard to crop water availability and so there is growing interest in the interaction between crop water regimes and fruit quality.

Several Mediterranean tomato landraces have two important traits for potential crop improvement: drought resistance and extended fruit shelf-life; however, little is known about the possible interactions between these factors the effect on fruit quality. Both traits are characteristic in the Ramellet tomato from the Balearic Islands (TdR), which have been selected over generations based on these traits. TdR plants have clearly adapted to allow to exhibit high water use efficiency. In addition, unlike many non-ripening mutants, TdR plants, as well as and the dfd (delayed fruit deterioration) mutant and the Penjar tomato, exhibit long shelf-life (LSL) phenotypes while retaining important ripening features. LSL has been associated with the alc mutation, although in TdR lines homozygous for alc, the shelf-life of only some lines was found to be substantially reduced when cultivated without water deficit.

The aims of our current studies of TdR are: i) to reveal the possible biomechanical, physiological or composition-related determinants of fruit traits within TdR accessions; and ii) to compare such behaviors and determine the mechanistic basis of the response to water stress in other LSL tomato varieties.

We expect that the outcomes of our studies will allow the detection of key traits that quantitatively or qualitatively underlie extended shelf-life in TdR, irrespective of the irrigation regime during cultivation. This may also determine, for other extended shelf-life tomatoes, the sensitivity of this trait to the cultivation method.

Julian K-C Ma (St. George’s Hospital Medical School, London UK) 

MOLECULAR PHARMING THE PRODUCTION OF RECOMBINANT PHARMACEUTICALS USING PLANT BIOTECHNOLOGY STILL A PALATABLE PROSPECT?

Most biopharmaceuticals are currently made at great expense in fermentation vats containing bacteria or mammalian cells. But the mass production of medicines in genetically modified plants, first proposed in 1989, coupled to early considerations of using edible crops for manufacture and delivery, could reduce costs and therefore make an important contribution to global health, particularly in developing countries.

Molecular Pharming has faced a number of challenges. There has been widespread scepticism that recombinant proteins could be manufactured in plants to the same standard and quality as current conventional systems. Developing a robust and reproducible manufacturing process for plants has therefore been an important priority for the field, an achievement that has recently been reached.

The concept of edible vaccines has required re-evaluation, to address immunological concerns, as well as those of regulators.

This talk will describe the rationale for developing GM plants for pharmaceutical production, the immunological constraints for oral delivery, and the key areas of concern for regulators in approving pharmaceutical manufacturing processes in plants, including the use of fruits and minimally processed plant preparations.

Cathie Martin (John Innes Center, UK)  

METABOLIC ENGINEERING OF ANTHOCYANINS IN TOMATO FRUIT ALLOWS FOR ASSESSMENT OF THEIR DIETARY HEALTH BENEFITS

Anthocyanins are pigments in plants that are increasingly being recognised as promoting human health when included in the diet. A combination of two transcription factors (Delia and Rosea 1) has been used to upregulate anthocyanin biosynthesis in tomato, resulting in purple tomatoes which extend the life span of cancer-prone p53 knock-out mice. Studies with breast cancer cell lines show that extracts of the purple tomatoes promote apoptosis compared to extracts from control, red tomatoes, indicating that the mechanism whereby dietary anthocyanins partially complement deficiencies in p53 activity may involve promotion of apoptosis in cancer cells.

We have extended our preclinical studies to examine the effects of high-anthocyanin diets on the ApoE mouse model of atherosclerosis. High anthocyanin diets reduced the formation of plaque and modified lipid metabolism, so reducing markers for the disease.

Given these positive results from studies of the protective effects of diets enriched in anthocyanins we have undertaken pilot cultivation of processing tomatoes with the high anthocyanin trait, prepared juice and we are initiating human intervention studies with subjects at risk of cardiovascular disease. We have also started notification of the FDA in the US, as the first step towards a commercial product available for human consumption.

Michele Morgante (University Udine, IT) 

FROM ONE TO THE MANY GENOMES OF GRAPEVINE: THE EVOLUTION OF THE GRAPEVINE PAN-GENOME

The analysis of variation in plants has revealed that their genomes are characterised by high levels of structural variation, consisting of both smaller insertion/deletions, mostly due to recent insertions of transposable elements, and of larger insertion/deletion similar to those termed in humans Copy Number Variants (CNVs). These observations indicate that a single genome sequence might not reflect the entire genomic complement of a species, and prompted us to introduce the concept of the plant pan-genome, including core genomic features common to all individuals and a Dispensable Genome (DG) composed of partially shared and/or non shared DNA sequences. The very active transposable element systems present in many plant genomes may account for a large fraction of the DG. The mechanisms by which the CNV-like variants are generated and the direction of the mutational events are still unknown. Uncovering the intriguing nature of the DG, i.e. its composition, origin and function, represents a step forward towards an understanding of the processes generating genetic diversity and phenotypic variation. Additionally, since the DG clearly appears to be for the most part the youngest and most dynamic component of the pan genome, it is of great interest to understand whether it is a major contributor to the creation of new genetic variation in plant evolution as well as in the artificial selection processes of plant breeding. We have resequenced to high coverage more than 50 grapevine accessions and used a variety of approaches to detect structural variants, including de novo assembly of a selected set of genotypes. We will discuss the extent and composition of the pan genome in grapevine, the different mechanisms that generate and maintain the dispensable portion, the epigenetic and phenotypic effects of the DG and the rates and modes of creation of new genetic variation due to DG components.

Nicola Patron (The Sainsbury Lab,  UK) 

PLANT GENOME ENGINEERING

Plant synthetic biology offers the means and opportunity to engineer plants and algae for new roles in our environment, to produce therapeutic compounds and to address global problems such as food insecurity and the contamination of ecosystems with agrochemicals and macronutrients. Such complex engineering requires standardized, automatable methods for assembling DNA as well as techniques for manipulating nuclear genomes. Random mutagenesis and gene-insertion methods are being superseded by genome editing technologies that enable precise manipulation of specific sequences. We are developing easily programmable molecular tools based on re-engineered CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas (CRISPR-associated) prokaryotic adaptive immune systems. Using these tools we can induce single and double stranded DNA breaks at pre-determined loci, thus activating the endogenous mechanisms of DNA repair. 

Pedro Rodriguez (IBMCP-CSIC, SP)

“BIOTECHNOLOGICAL APPROACHES FOR ENHANCING PLANT DROUGHT RESISTANCE BASED ON FUNDAMENTAL RESEARCHES IN ABA SIGNALING”

Plant stress biology faces several key challenges, particularly the generation of new crop varieties with improved water use efficiency and drought resistance. ABA receptors engineered to enhance ABA-dependent inhibition of protein phosphatases type 2C do have biotechnological potential to enhance plant drought resistance (Pizzio et al., 2013). In order to demonstrate the efficacy of mutant ABA receptors in crop plants, we generated barley transgenic plants that over-express mutant versions of Arabidopsis PYL4 receptors. As a result, we found that barley transformed plants that express PYL4^A194T orPYL4^{H82R V97A} showed enhanced drought tolerance and therefore, we describe a novel technology to cope with water stress. We have also identified the full set of tomatoABA receptors, which were functional in Arabidopsis plant cells and over-expression of two monomeric-type receptors conferred enhanced drought resistance. Additionally, chemical approaches based on recently identified ABA-agonists, such as quinabactin, or orthogonal ligand-receptor activation of ABA signaling might have biotechnological use in crops.

Auxiliary proteins that regulate half-life, trafficking or membrane targeting of ABA receptors also represent potential sources of candidate genes to modulate ABA signaling.  We have identified a gene family, named RSL1/RFA, of single subunit E3 ubiquitin ligases that act as E3 ligases of ABA receptors and therefore control their ubiquitylation and half-life (Bueso et al., 2014). Targeting of ABA receptors by different RSL1/RFA E3s occurs at different cell compartments, which illustrates a novel mechanism to promote the turnover of ABA receptors -and attenuate ABA perception- in plasma membrane, cytosol and nucleus.  We have also discovered that calcium-dependent interaction of ABA receptors with membranes is mediated through a new gene family of C2-domain ABA-related (CAR) proteins (Rodriguez et al., 2014). The function of ABA receptors in plasma membrane is eventually modulated through the RSL1 E3 ligase, which targets ABA receptors there and promotes their degradation.