177,325 research outputs found
Paramutation : Just a Curiosity or Fine Tuning of Gene Expression in the Next Generation?
No full textGene silencing is associated with heritable changes in gene expression which occur without changes in DNA sequence. In eukaryotes these phenomena are common and control important processes, such as development, imprinting,viral and transposon sequence silencing, as well as transgene silencing. Among the epigenetic events, paramutation occurs when a silenced allele (named paramutagenic) is able to silence another allele (paramutable) in trans and this change is heritable. The silenced paramutable allele acquires paramutagenic capacity in the next generations. In the 1950s, Alexander Brink described for the first time the phenomenon of paramutation, occurring in maize at the colored1 (r1) gene, a complex locus (encoding myc-homologous transcription factors) that regulates the anthocyanin biosynthetic pathway. Since then, paramutation and paramutation-like interactions have been discovered in other plants and animals, suggesting that they may underlie important echanisms for gene expression. The molecular bases of these phenomena are unknown. However in some cases, the event of paramutation has been correlated with changes in NA methylation, chromatin structure and recently several studies suggest that RNA could play a fundamental role. This last consideration is greatly supported by genetic screening for mutants inhibiting paramutation, which allowed the identification of genes involved in RNA-directed transcriptional silencing, although it is possible that proteins are also equired for paramutation. The meaning of paramutation in the life cycle and in evolution remains to be determined even though we might conjecture that this phenomenon could be involved in a fast heritability of favourable epigenetic states across generations in a non-Mendelian way
Paramutation phenomena in plants
No full textParamutation is a particular epigenetic phenomenon discovered in Zea mays by Alexander Brink in the 1950s, and then also found in other plants and animals. Brink coined the term paramutation (from the Greek syllable "para" meaning beside, near, beyond, aside) in 1958, with the aim to differentiate paramutation from mutation. The peculiarity of paramutation with respect to other gene silencing phenomena consists in the ability of the silenced allele (named paramutagenic) to silence the other allele (paramutable) present in trans. The newly silenced (paramutated) allele remains stable in the next generations even after segregation from the paramutagenic allele and acquires paramutagenic ability itself. The inheritance behaviour of these epialleles permits a fast diffusion of a particular gene expression level/phenotype in a population even in the absence of other evolutionary influences, thus breaking the Hardy-Weinberg law. As with other gene silencing phenomena such as quelling in the fungus Neurospora crassa, transvection in Drosophila, co-suppression and virus-induced gene silencing (VIGS) described in transgenic plants and RNA interference (RNAi) in the nematode Caenorhabditis elegans, paramutation occurs without changes in the DNA sequence. So far the molecular basis of paramutation remains not fully understood, although many studies point to the involvement of RNA causing changes in DNA methylation and chromatin structure of the silenced genes. In this review I summarize all paramutation phenomena described in plants, focusing on the similarities and differences between them
Caratterizzazione e tutela di un'antica varietà di montagna: il Mais Nero Spinoso di Valle Camonica
No full textLa varietà della specie Zea mays denominata Mais Nero Spinoso di Valle Camonica è tradizionalmente coltivata nei territori comunali di Esine, Piancogno e limitrofi (Val Camonica, BS). Testimonianze dirette da parte di alcuni agricoltori, riportano la coltivazione di questa varietà di mais tra la fine del XIX e gli inizi del XX secolo in località Annunciata del Comune di Piancogno. Essa può quindi essere considerata una varietà locale come indicato dalle linee guida nazionali per la conservazione della biodiversità vegetale (Decreto del Ministero delle Politiche Agricole, Alimentari e Forestali del 6 luglio 2012).
La granella prodotta, di colore bruno/nero, è caratterizzata da una evidente spinatura ed è stata (e lo è tuttora) utilizzata principalmente per la produzione di farina da polenta ad uso prevalentemente familiare. La varietà si presta particolarmente alla coltivazione in ambiente montano, anche a quote superiori ai 1000 metri, grazie alla sua rusticità e alla lunghezza media del ciclo vegetativo. Durante la seconda metà del XX secolo la coltivazione di questa varietà, che era in precedenza diffusa tra gli agricoltori della madia Val Camonica, è stata quasi del tutto abbandonata, complici l’avvento degli ibridi commerciali e la riduzione del consumo di polenta, alimento che è stato per secoli alla base dell’alimentazione della popolazione contadina. In seguito ai recenti studi condotti dall' "Università della Montagna" (Ge.S.Di.Mont.), la coltivazione del Mais Nero Spinoso di Valle Camonica ha trovato nuovo impulso, suscitando l’interesse di alcuni agricoltori locali. Ciononostante il rischio che tale varietà finisca per essere completamente abbandonata o possa ibridarsi rimane tuttora.
La varietà presenta un’elevata rilevanza dal punto di vista fitogenetico in virtù delle sue peculiari caratteristiche morfologiche e fenotipiche, e in particolare per la sua granella dalla caratteristica forma rostrata e dalla pigmentazione bruna che, a differenza di altre varietà di mais, non è dovuta all’accumulo di antocianine ma alla presenza di flobafeni nel pericarpo. Tali pigmenti sono sintetizzati in mais attraverso la via dei flavonoidi mediante la polimerizzazione dei flavan-4-ols, guidata dalla presenza del gene regolatore P1 (pericarp color1). Varietà di mais recanti il gene P1 e capaci di accumulare elevate quantità di flobafeni nel pericarpo della granella, possono rappresentare una risorsa dal momento che i flobafeni possiedono proprietà antiossidanti capaci di prevenire malattie croniche (Casas et al., 2014). Inoltre sembrerebbe che le varietà portanti il gene P1 possano essere meno suscettibili all’accumulo di micotossine (Pilu et al., 2011). Al fine di tutelare tale varietà e quindi l'agrobiodiversità, l' "Università della Montagna" (congiuntamente ai comini di Esine e Piancogno) ad aprile 2015 ha avviato le pratiche per il suo inserimento nella sezione "varietà da conservazione" del Registro Nazionale di Specie Agrarie e Orticole (D.M. 17 dicembre 2010)
Il fosforo e l'acido fitico in agricoltura: implicazioni dal punto di vista alimentare ed ambientale
No full textArundo donax as an energy crop: pros and cons of the utilization of this perennial plant.
No full textArundo donax (giant reed) is a rhizomatous grass widely found in temperate and subtropical regions. Because of its capacity to grow vigorously in marginal land, it is considered as a dangerous weed plant. However, humans contributed to the dispersion of this plant around the world because Arundo is used it for multiple purposes such as reeds in woodwind musical instruments, roof thatching and fishing rods. In recent years A. donax, due to its high biomass production has been also considered as a promising energy crop. Nevertheless, some important issues must be addressed. In fact, A. donax is a sterile plant and its propagation is based on vegetative propagation (fragmentation of rhizomes or canes) and in vitro culture, making establishing the crop on a large scale very expensive. Furthermore the geneticists cannot carry out conventional breeding programmes, so improvement will be based on ecotype selection, chemical and physical mutagenesis, and transgenesis techniques. Another aspect to consider for a massive utilization of A. donax as an energy crop consists in the scarcity of data on long-term field experiments, since the duration of the crop's life is 12-15 years. Hence, in this short review, we will bring together the principal pros and cons of this new putative energy crop
Characterization of the Ra1 maize gene involved in inflorescence architecture
No full textThe genetic and molecular control of inflorescence and flower development has been extensively studied in model dicotyledonous plants such as Arabidopsis but even now little is known about monocotyledonous species. In maize several mutants have been isolated that perturbed normal inflorescence development. In particular, the Ramosa1 (Ra1) gene, coding for a zinc finger transcription factor, plays a role in inflorescence structure by determining the number of branches. Although the mechanism by which Ra1 acts is unclear, inflorescence meristems in these regions assume a branch meristem identity rather than becoming spikelet pairs.
In this work we characterize a new mutation of Ra1 gene that originated spontaneously from a B73 inbred line.
This loss-of-function mutation is caused by the deletion of the lysine residue at position 53 in the RA1 putative zinc-finger domain. This is the first evidence for a single amino acid deletion in the zinc finger domain that knocks out the function of the RA1 protein. This result strongly suggests that the RA1 protein functions by acting as a DNA-binding protein, probably involved in transcriptional regulation. Furthermore, Ra1 overexpression in the Arabidopsis ortholog superman (sup) mutant, whose flowers are characterized by the presence of additional stamens, was not able to restore the correct stamen number, indicating that SUP and Ra1 genes do not share an identical function
Arabidopsis thaliana plants overexpressing Ramosa1 maize gene show an increase in organ size due to cell expansion
No full textThe structure of the plant inflorescence and flower is an important agronomic and ornamental trait studied for its potential economic applications. In particular, the capacity to modify flower size has always been a breeder's goal. Genetic and molecular studies have shown that the Zea mays gene Ramosa1 (Ra1) is involved in inflorescence branching regulation. In fact the ra1 loss of function mutation causes extra branching of the inflorescence. In this work we suggest a possible utilization of the Ramosa1 maize gene as a tool to modify inflorescence architecture and flower size in transgenic plants. In fact overexpression of this gene in Arabidopsis plants promotes an increase in reproductive organ size. Pollen, seeds, cotyledons, leaves and roots are also larger than those of the wild type. Analysis of organs from transformants showed that cell expansion was increased without apparently affecting cell division. These results suggest that the RA1 protein is able to up-regulate cell expansion in all organs of Arabidopsis plants
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