Fruit set is an essential process to ensure successful sexual plant reproduction. The development of the flower into a fruit is actively repressed in the absence of pollination. However, some cultivars from a few species are able to develop seedless fruits overcoming the standard restriction of unpollinated ovaries to growth. We report here the identification of the tomato hydra mutant that produces seedless (parthenocarpic) fruits. Seedless fruit production in hydra plants is linked to the absence of both male and female sporocyte development. The HYDRA gene is therefore essential for the initiation of sporogenesis in tomato. Using positional cloning, virus-induced gene silencing and expression analysis experiments, we identified the HYDRA gene and demonstrated that it encodes the tomato orthologue of SPOROCYTELESS/NOZZLE (SPL/NZZ) of Arabidopsis. We found that the precocious growth of the ovary is associated with changes in the expression of genes involved in gibberellin (GA) metabolism. Our results support the conservation of the function of SPL-like genes in the control of sporogenesis in plants. Moreover, this study uncovers a new function for the tomato SlSPL/HYDRA gene in the control of fruit initiation.

SUMMARY Legumes have unique features, such as compound inflorescences and a complex floral ontogeny. Thus, the study of regulatory genes in these species during inflorescence and floral development is essential to understand their role in the evolutionary origin of developmental novelties. The SUPERMAN (SUP) gene encodes a C2H2 zinc‐finger transcriptional repressor that regulates the floral organ number in the third and fourth floral whorls of Arabidopsis thaliana. In this work, we present the functional characterization of the Medicago truncatula SUPERMAN (MtSUP) gene based on gene expression analysis, complementation and overexpression assays, and reverse genetic approaches. Our findings provide evidence that MtSUP is the orthologous gene of SUP in M. truncatula. We have unveiled novel functions for a SUP‐like gene in eudicots. MtSUP controls not only the number of floral organs in the inner two whorls, but also in the second whorl of the flower. Furthermore, MtSUP regulates the activity of the secondary inflorescence meristem, thus controlling the number of flowers produced. Our work provides insight into the regulatory network behind the compound inflorescence and flower development in this angiosperm family.

BackgroundPlants and insects have coexisted for million years and evolved a set of interactions which affect both organisms at different levels. Plants have developed various morphological and biochemical adaptations to cope with herbivores attacks. However, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has become the major pest threatening tomato crops worldwide and without the appropriated management it can cause production losses between 80 to 100%.ResultsThe aim of this study was to investigate the in vivo effect of a serine proteinase inhibitor (BTI-CMe) and a cysteine proteinase inhibitor (Hv-CPI2) from barley on this insect and to examine the effect their expression has on tomato defensive responses. We found that larvae fed on tomato transgenic plants co-expressing both proteinase inhibitors showed a notable reduction in weight. Moreover, only 56% of these larvae reached the adult stage. The emerged adults showed wings deformities and reduced fertility. We also investigated the effect of proteinase inhibitors ingestion on the insect digestive enzymes. Our results showed a decrease in larval trypsin activity. Transgenes expression had no harmful effect on Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae), a predator of Tuta absoluta, despite transgenic tomato plants attracted the mirid. We also found that barley cystatin expression promoted plant defense by inducing the expression of the tomato endogenous wound inducible Proteinase inhibitor 2 (Pin2) gene, increasing the production of glandular trichomes and altering the emission of volatile organic compounds.ConclusionOur results demonstrate the usefulness of the co-expression of different proteinase inhibitors for the enhancement of plant resistance to Tuta absoluta.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1240-6) contains supplementary material, which is available to authorized users.

Genetic engineered male sterility has different applications, ranging from hybrid seed production to bioconfinement of transgenes in genetic modified crops. The impact of this technology is currently patent in a wide range of crops, including legumes, which has helped to deal with the challenges of global food security. Production of engineered male sterile plants by expression of a ribonuclease gene under the control of an anther- or pollen-specific promoter has proven to be an efficient way to generate pollen-free elite cultivars. In the last years, we have been studying the genetic control of flower development in legumes and several genes that are specifically expressed in a determinate floral organ were identified. Pisum sativum ENDOTHECIUM 1 ( PsEND1 ) is a pea anther-specific gene displaying very early expression in the anther primordium cells. This expression pattern has been assessed in both model plants and crops (tomato, tobacco, oilseed rape, rice, wheat) using genetic constructs carrying the PsEND1 promoter fused to the uidA reporter gene. This promoter fused to the barnase gene produces full anther ablation at early developmental stages, preventing the production of mature pollen grains in all plant species tested. Additional effects produced by the early anther ablation in the PsEND1 :: barnase-barstar plants, with interesting biotechnological applications, have also been described, such as redirection of resources to increase vegetative growth, reduction of the need for deadheading to extend the flowering period, or elimination of pollen allergens in ornamental plants ( Kalanchoe, Pelargonium ). Moreover, early anther ablation in transgenic PsEND1::barnase-barstar tomato plants promotes the developing of the ovaries into parthenocarpic fruits due to the absence of signals generated during the fertilization process and can be considered an efficient tool to promote fruit set and to produce seedless fruits. In legumes, the production of new hybrid cultivars will contribute to enhance yield and productivity by exploiting the hybrid vigor generated. The PsEND1::barnase-barstar construct could be also useful to generate parental lines in hybrid breeding approaches to produce new cultivars in different legume species.

The development of antibiotic resistance in the opportunistic pathogen Pseudomonas aeruginosa is a major cause of the pathogen's morbidity and is strongly correlated with the biofilm formation. Motility and adherence capacity in long-term stressed cells have not been extensively analyzed even though P. aeruginosa considered a model organism for the study of biofilm formation. In this investigation, P. aeruginosa ATCC 27853 strain has been stored for 12 months in LB broth with 0.5 M NaCl. Several experiments demonstrated that the strain recovery from the salty microcosm had the ability to increase the biofilm formation and to reduce motility comparing with that of the original strain. To identify genes involved in the regulation of biofilm and/or in stress response by the recovered P. aeruginosa, differential display "DDRT-PCR" technique was used. The genes speD and ccoN2, coding, respectively, for an S-adenosylmethionine decarboxylase and Cbb3-type cytochrome oxidase, were identified in recovered strain of P. aeruginosa ATCC 27853 as two differentially expressed gene fragments. A comparison of the biofilm produced by the wild-type strain PA14 and the transposon insertion mutant for speD gene suggested that spermidine has a potential role in the adaptive response in P. aeruginosa incubated in long-term stress conditions.