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Annonaceae represent the largest extant family among the early divergent angiosperms. Despite the long-standing interest in its evolutionary and taxonomic aspects, cytogenetic studies on this family remain extremely few even on economically important species. With this study, we realized a detailed characterization of the chromosomes of Annona cherimola (2n = 14) by a combination of in situ hybridization techniques, fluorochrome banding, and karyomorphological analysis. FISH revealed that 45S and 5S rDNA sites are co-localized in correspondence to the secondary constrictions of the SAT-chromosome pair. Some hypotheses on the organization of the linked 45S and 5S rDNA repeats have been made. FISH with Arabidopsis-type telomeric arrays demonstrated that the A. cherimola telomeres are constituted by TTTAGGG sequences and that they are exclusively localized at the extremities of chromosomes. An insight into the chromosome structure of A. cherimola was obtained by the self-GISH procedure which revealed highly repeated DNA sequences localized in the centromeric regions of all chromosomes. The correspondence of s-GISH signals with DAPI banding suggests that these sequences are the principal component of the centromeric heterochromatin of this species. The karyotype of A. cherimola here described is proposed as the basic reference karyotype for successive investigations in Annonaceae. Key words: Annona cherimola, karyotyping, FISH, GISH, telomeres, ribosomal genes, repetitive DNA. Résumé: Les Annonacées constituent la plus grande famille existante parmi les angiospermes primitives. En dépit d'un intérêt de longue date portant sur les aspects évolutifs et taxonomiques, les études cytogénétiques au sein de cette famille sont très peu nombreuses, même chez les espèces d'importance économique. Dans ce travail, les auteurs ont réalisé une caractérisation détaillée des chromosomes chez l'Annona cherimola (2n = 14) en combinant diverses approches d'hybridation in situ, de coloration des bandes à l'aide de fluorochromes et une analyse caryo-morphologique. Les analyses FISH ont révélé que les sites d'ADNr 45S et 5S co-localisent avec les sites de constriction secondaire chez la paire de chromosomes SAT. Certaines hypothèses sur l'organisation des répétitions liées d'ADNr 45S et 5S ont été formulées. Les analyses FISH au moyen des répétitions télomériques du type retrouvé chez Arabidopsis ont permis de démontrer que les télomères de l'A. cherimola sont constitués de séquences TTTAGGG et que ces séquences sont uniquement présentes aux extrémités des chromosomes. Un aperçu de la structure des chromosomes chez l'A. cherimola a été obtenu au moyen d'une approche auto-GISH, laquelle a révélé que des séquences très fortement répétées sont localisées au sein des régions centromériques de tous les chromosomes. La proche correspondance entre les signaux s-GISH et les bandes colorées au DAPI suggère que ces séquences constituent la principale composante de l'hétérochromatine chez cette espèce. Les auteurs proposent le caryotype de l'A. cherimola décrit dans ce travail comme caryotype de référence de base pour les futures investigations chez les Annonacées. [Traduit par la Rédaction] Mots-clés : Annona cherimola, caryotypage, FISH, GISH, télomères, gènes ribosomiques, ADN répété., Introduction The Annonaceae are a pantropical family of flowering trees, shrubs, and lianas, predominantly growing in tropical and subtropical ecosystems where they play an important ecological role in terms of [...]

Saffron is one of the most highly priced agricultural products in the world. Its prize can reach 20,000 €/kg retail and this is due both to the high demand and to the great cultivation and production costs. Several studies have demonstrated that differences in saffron quality are mainly due to the methodology followed in the processing of stigmas, and environmental conditions independent of the origin. Some authors found phenotypic variations within cultivated saffron, but very limited genetic diversity. The reason for the very limited genetic diversity in cultivated saffron is explained by its asexual mode of reproduction (propagation). The aim of this study was to assess the antimicrobial activity of stigma saffron, which were tested against different bacteria strains. The results obtained from the antimicrobial activity study indicate that stigmas of C. sativus have some antimicrobial effect. [ABSTRACT FROM AUTHOR]

The molecular mechanisms of transferred DNA (T-DNA) integration into the plant genome are still not completely understood. A large number of integration events have been analyzed in different species, shedding light on the molecular mechanisms involved, and on the frequent transfer of vector sequences outside the T-DNA borders, the so-called vector backbone (VB) sequences. In this work, we characterized 46 transgenic alfalfa (Medicago sativa L.) plants (events), generated in previous works, for the presence of VB tracts, and sequenced several T-DNA/genomic DNA (gDNA) junctions. We observed that about 29% of the transgenic events contained VB sequences, within the range reported in other species. Sequence analysis of the T-DNA/gDNA junctions evidenced larger deletions at LBs compared to RBs and insertions probably originated by different integration mechanisms. Overall, our findings in alfalfa are consistent with those in other plant species. This work extends the knowledge on the molecular events of T-DNA integration and can help to design better transformation protocols for alfalfa. [ABSTRACT FROM AUTHOR]

Polyploidization as the consequence of 2n gamete formation is a prominent mechanism in plant evolution. Studying its effects on the genome, and on genome expression, has both basic and applied interest. We crossed two diploid (2n = 2x = 16) Medicago sativa plants, a subsp. falcata seed parent, and a coerulea × falcata pollen parent that form a mixture of n and 2n eggs and pollen, respectively. Such a cross produced full-sib diploid and tetraploid (2n = 4x = 32) hybrids, the latter being the result of bilateral sexual polyploidization (BSP). These unique materials allowed us to investigate the effects of BSP, and to separate the effect of intraspecific hybridization from those of polyploidization by comparing 2x with 4x full sib progeny plants. Simple sequence repeat marker segregation demonstrated tetrasomic inheritance for all chromosomes but one, demonstrating that these neotetraploids are true autotetraploids. BSP brought about increased biomass, earlier flowering, higher seed set and weight, and larger leaves with larger cells. Microarray analyses with M. truncatula gene chips showed that several hundred genes, related to diverse metabolic functions, changed their expression level as a consequence of polyploidization. In addition, cytosine methylation increased in 2x, but not in 4x, hybrids. Our results indicate that sexual polyploidization induces significant transcriptional novelty, possibly mediated in part by DNA methylation, and phenotypic novelty that could underpin improved adaptation and reproductive success of tetraploid M. sativa with respect to its diploid progenitor. These polyploidy-induced changes may have promoted the adoption of tetraploid alfalfa in agriculture., (Copyright © 2016 Rosellini et al.)

Antibiotic-free, efficient in vitro selection in plant genetic engineering can improve risk perception and speed up pre-market scrutiny of genetically modified crops. We provide a protocol for genetic transformation of two important crops, durum wheat and alfalfa, using a bacterial and a plant-derived selectable marker gene encoding mutated, gabaculine-insensitive glutamate 1-semialdehyde aminotransferase (GSA) enzymes. These methods can potentially be applied, with minor adaptations, to many other monocot and dicot crop plants.