Ovule development, a new model for lateral organ formation

In spermatophytes the ovules upon fertilization give rise to the seeds. It is essential to understand the mechanisms that control ovule number and development as they ultimately determine the final number of seeds and, thereby, the yield in crop plants. In Arabidopsis thaliana, ovules arise laterally from a meristematic tissue within the carpel referred to as placentaMara Cucinotta was funded by a Ph.D fellowshipfrom the Università degli Studi di Milano, Irma Roig-Villanovawas funded by MIUR-Fondo per gli Investimenti della Ricerca diBase-Futuro in Ricerca. The work of Lucia Colombo is supportedby MIUR-PRIN 2012Postprint (published version

Plant Responses to Vegetation Proximity: A Whole Life Avoiding Shade

In high density of vegetation, plants detect neighbors by perceiving changes in light quality through phytochrome photoreceptors. Close vegetation proximity might result in competition for resources, such as light. To face this challenge, plants have evolved two alternative strategies: to either tolerate or avoid shade. Shade-avoiding species generally adapt their development by inducing hypocotyl, stem, and petiole elongation, apical dominance and flowering, and decreasing leaf expansion and yield, a set of responses collectively known as the shade avoidance syndrome (SAS). The SAS responses have been mostly studied at the seedling stage, centered on the increase of hypocotyl elongation. After compiling the main findings about SAS responses in seedlings, this review is focused on the response to shade at adult stages of development, such as petioles of adult leaves, and the little information available on the SAS responses in reproductive tissues. We discuss these responses based on the knowledge about the molecular mechanisms and components with a role in regulating the SAS response of the hypocotyls of Arabidopsis thaliana. The transcriptional networks involved in this process, as well as the communication among the tissues that perceive the shade and the ones that respond to this stimulus will also be briefly commented.IR-V holds a Beatriu de Pinós contract from the Agència de Gestió D’Ajuts Universitaris i de Recerca (AGAUR, Generalitat de Catalunya). Our research is supported by grants from the Spanish Ministerio de Economía y Competitividad (BIO2014-59895-P) and AGAUR (2014-SGR447 and Xarba) to JFM-G.Peer reviewedPeer Reviewe

Current perspectives on the hormonal control of seed development in Arabidopsis and maize: a focus on auxin.

The seed represents the unit of reproduction of flowering plants, capable of developing into another plant, and to ensure the survival of the species under unfavorable environmental conditions. It is composed of three compartments: seed coat, endosperm and embryo. Proper seed development depends on the coordination of the processes that lead to seed compartments differentiation, development and maturation.Funded by the Ministry for Education and University, Italy(FIRB grant no. RBFR08UG7)Postprint (published version

Light signaling: back to space

Recent work has increased our understanding of the molecular and cellular mechanisms of the phytochrome family of photoreceptors in controlling plant photomorphogenesis. However, the importance of long-distance communication in controlling light responses has received relatively little attention and is poorly understoodPostprint (author's final draft

Early cold stress responses in post-meiotic anthers from tolerant and sensitive rice cultivars

Background: Rice grain production is susceptible to a changing environment that imposes both biotic and abiotic stress conditions. Cold episodes are becoming more frequent in the last years and directly affect rice yield in areas with a temperate climate. Rice is particularly susceptible to cold stress during the reproductive phase, especially in anthers during post-meiotic stages which, in turn, affect pollen production. However, a number of rice cultivars with a certain degree of tolerance to cold have been described, which may represent a good breeding resource for improvement of susceptible commercial varieties. Plants experiencing cold stress activate a molecular response in order to reprogram many metabolic pathways to face these hostile conditions. Results: Here we performed RNA-seq analysis using cold-stressed post-meiotic anther samples from a cold-tolerant, Erythroceros Hokkaido (ERY), and a cold-susceptible commercial cultivar Sant’Andrea (S.AND). Both cultivars displayed an early common molecular response to cold, although the changes in expression levels are much more drastic in the tolerant one. Comparing our datasets, obtained after one-night cold stress, with other similar genome-wide studies showed very few common deregulated genes, suggesting that molecular responses in coldstressed anthers strongly depend on conditions and the duration of the cold treatments. Cold-tolerant ERY exhibits specific molecular responses related to ethylene metabolism, which appears to be activated after cold stress. On the other hand, S.AND cold-treated plants showed a general downregulation of photosystem I and II genes, supporting a role of photosynthesis and chloroplasts in cold responses in anthers, which has remained elusive. Conclusions: Our study revealed that a number of ethylene-related transcription factors, as putative master regulators of cold responses, were upregulated in ERY providing promising candidates to confer tolerance to susceptible cultivars. Our results also suggest that the photosynthesis machinery might be a good target to improve cold tolerance in anthers. In summary, our study provides valuable candidates for further analysis and molecular breeding for cold-tolerant rice cultivars.Fil: Gonzalez Schain, Nahuel Damian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Roig Villanova, Irma. Università degli Studi di Milano; ItaliaFil: Kater, Martin M.. Università degli Studi di Milano; Itali

Seed abscission and fruit dehiscence required for seed dispersal rely on similar genetic networks

Seed dispersal is an essential trait that enables colonization of newfavorable habitats, ensuring species survival. In plants with dehiscentfruits, such asArabidopsis, seed dispersal depends on two processes:the separation of the fruit valves that protect the seeds (fruitdehiscence) and the detachment of the seeds from the funiculusconnectingthemtothe motherplant (seed abscission).Postprint (published version

Millora de varietats tradicionals de tomàquet

Les varietats tradicionals de tomàquet constitueixen un recurs important per les explotacions hortícoles ecològiques, tant per la seva adaptació a condicions d’una agricultura de baixa intensitat, com per les seves característiques culturals i culinàries. La seva presència en camps de cultiu comercials és, però, escassa, degut principalment a la seva sensibilitat a les plagues i malalties que afecten a l’espècie, així com en molts casos a la seva baixa productivitat. El mètode més efectiu de control d’algunes malalties com les virosis és la resistència genètica, la qual és present en la major part de varietats millorades. Introduir aquests gens de resistència en les varietats tradicionals pot ser una estratègia per revifar el seu cultiu i recuperar la diversitat varietal autòctona. Amb aquest objectiu s’està impulsant un programa de millora genètica per tal d’incorporar la resistència a virosis, fongs i nematodes en una línia tradicional del tomàquet Pera de Girona. El programa de millora s’està realitzant seguint diferents línies de treball. Els resultats de l’any 2020, han permès identificar 11 genotips resistents al virus del bronzejat (TSWV), un dels quals també té resistència a nematodes, que es troben en una generació avançada de desenvolupament (BC2S4). Aquests materials seran sotmesos a un procés de selecció participativa l’any 2021. Paral·lelament es disposa de materials en estadis avançats de desenvolupament per aconseguir obtenir varietats resistents a la resta de patògens que limiten el cultiu de les varietats tradicionals de tomàquetPostprint (published version

Breeding long shelf-life (LSL) tomato landraces to non-trellised culture and water deficit irrigation: the effect on yield and postharvest storage

Non-trellised culture of tomato is gaining interest among farmers cultivating long shelf-life (LSL) landraces because of the reduction in production costs. This cropping system can benefit from the selection of determinate growth genotypes, mirroring the advancements achieved in processing tomatoes. With this aim, and profiting from the natural variation found within the Penjar landrace, we selected traditional determinate genotypes and breed novel lines carrying both the self-pruning (sp) and the compound inflorescence (s) mutations. Traditional genotypes and breeding lines were compared to commercial controls in a three multi-locality trial and under two irrigation regimes (normal watered, 100% ETc; and water deficit, 50% ETc). Water use efficiency, harvest index, yield and fruit quality traits were studied at harvest. During postharvest, the effects of genotype and management practices on shelf life were assessed under different storage conditions (controlled conditions/cold storage/farmer facilities). All genotypes used water more efficiently under water deficit irrigation than under normal irrigation. Harvest index was improved in the determinate genotypes and was neither affected by locality nor by irrigation factors. Breeding lines showed yields similar to the controls and the traditional ones; however, they displayed a plant architecture that facilitated their management. They also presented higher postharvest shelf life than controls and traditional lines. Shelf life was significantly affected by genotype (G), locality (L, at early stages), and irrigation regime (I, at later stages), with the contribution of the genotype to the phenotypic variance increasing along the postharvest. Low watering increased shelf life in some genotypes while cold storage and high humidity conditions impeded the long shelf-life trait. Overall, sunscald incidence and percentage of unripe fruits when using a single harvest strategy are the major limitations for non-trellised culture of Penjar tomato. In conclusion, this study sheds light on the main aspects of management and on breeding targets to promote a non-trellised culture of Penjar tomato in combination with optimal water use efficiency.This work was supported by the Department of Agriculture of Generalitat de Catalunya through the Technology Transfer program of the Rural Development Plan (2014–2020) (grant number 56 30018 2018 5A). Joan Casals and Irma Roig-Villanova are Serra Húnter fellows at Universitat Politècnica de CatalunyaPostprint (published version

A novel high-throughput in vivo molecular screen for shade avoidance mutants identifies a novel phyA mutation

The shade avoidance syndrome (SAS) allows plants to anticipate and avoid shading by neighbouring plants by initiating an elongation growth response. The phytochrome photoreceptors are able to detect a reduction in the red:far red ratio in incident light, the result of selective absorption of red and blue wavelengths by proximal vegetation. A shade-responsive luciferase reporter line (PHYB::LUC) was used to carry out a high-throughput screen to identify novel SAS mutants. The dracula 1 (dra1) mutant, that showed no avoidance of shade for the PHYB::LUC response, was the result of a mutation in the PHYA gene. Like previously characterized phyA mutants, dra1 showed a long hypocotyl in far red light and an enhanced hypocotyl elongation response to shade. However, dra1 additionally showed a long hypocotyl in red light. Since phyB levels are relatively unaffected in dra1, this gain-of-function red light phenotype strongly suggests a disruption of phyB signalling. The dra1 mutation, G773E within the phyA PAS2 domain, occurs at a residue absolutely conserved among phyA sequences. The equivalent residue in phyB is absolutely conserved as a threonine. PAS domains are structurally conserved domains involved in molecular interaction. Structural modelling of the dra1 mutation within the phyA PAS2 domain shows some similarity with the structure of the phyB PAS2 domain, suggesting that the interference with phyB signalling may be the result of non-functional mimicry. Hence, it was hypothesized that this PAS2 residue forms a key distinction between the phyA and phyB phytochrome species