Paramutation: Just a Curiosity or Fine Tuning of Gene Expression in the Next Generation?

Gene 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 mechanisms 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 DNA 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 required for paramutation

Morphological diversity among local and introduced maize (Zea mays L.) varieties in Haiti for yield improvement

Maize, the cereal with the largest production in the world, is a staple crop in many developing countries includingHaiti. Even if Haiti is the second maize consumer in the Caribbean region, its national yield is low and alleged ofaflatoxin contamination. In order to increase grain yield, three introduced and two local maize varieties (theseused as comparative control) were evaluated. Three field trials were carried out at Torbeck and Morne Briller (Port-Salut) during different growing seasons. Experiments were designed in a three-replicate randomized block. Eachexperimental plot was 3.50 m per 10.5 m with a gross area of 36.75 m2 and 40 000 plants/ha densities. The trialswere carried out according to local agricultural practices. The results revealed that the introduced varieties hada smaller yield than the local ones. Moreover, all varieties showed some aflatoxin content below the EuropeanUnion limit (5μg/Kg). Statistical analyses showed a strong and direct correlation between yield and ear weightand an inverse correlation between yield and male and female flowering day after sowing. The broad phenotypicdiversity suggested a rich reserve of alleles to exploit in a breeding program focused to improve food security inHaiti

A defective ABC transporter of the MRP family, responsible for the bean lpa1 mutation, affects the regulation of the phytic acid pathway, reduces seed myo-inositol and alters ABA sensitivity

We previously identified the lpa1 (low phytic acid) 280-10 line that carries a mutation conferring a 90% reduction in phytic acid (InsP6) content. In contrast to other lpa mutants, lpa1(280-10) does not display negative pleiotropic effects. In the present paper, we have identified the mutated gene and analysed its impact on the phytic acid pathway. Here, we mapped the lpa1(280-10) mutation by bulk analysis on a segregating F2 population, an then, by comparison with the soybean genome, we identified and sequenced a candidate gene. The InsP6 pathway was analysed by gene expression and quantification of metabolites. The mutated Pvmrp1(280-10) cosegregates with the lpa1(280-10) mutation, and the expression level of several genes of the InsP6 pathway are reduced in the lpa1(280-10) mutant as well as the inositol and raffinosaccharide content. PvMrp2, a very similar paralogue of PvMrp1 was also mapped and sequenced. The lpa1 mutation in beans is likely the result of a defective Mrp1 gene (orthologous to the lpa genes AtMRP5 and ZmMRP4), while its Mrp2 paralog is not able to complement the mutant phenotype in the seed. This mutation appears to down-regulate the InsP6 pathway at the transcriptional level, as well as altering inositol-related metabolism and affecting ABA sensitivity

Arundo donax as an energy crop: pros and cons of the utilization of this perennial plant

Arundo 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

Development and characterization of a coloured sweet corn line as a new functional food

The standard sugary sweet corn (Zea mays saccharata Sturt.) is a maize variety grown for the fresh, frozen and canned markets, traditionally appreciated. Its kernels are characterized by the presence of some antioxidant substances suggested to be beneficial for cancer prevention. For this reason an interesting challenge for breeders is the development of sweet corn genotypes with naturally high antioxidant levels, starting from flavonoids. In fact important sources of antioxidants in maize are anthocyanins, considered as nutraceuticals because they have been proven to lower the risk of many chronic diseases. In this paper we report the development of a new coloured sugary line and the results of some analyses concerning flavonoid content before and after two different cooking treatments are discussed. Attention was mainly focused on the anthocyanins, the molecules suggested as being responsible for the nutraceutical properties of the new coloured sugary line. The results show that the presence of the anthocyanins also pushes up the flavonol and the phenolic acid amounts and gives the new coloured sugary line a higher scavenging power compared to the uncoloured control. The mild cooking seems not to significantly change the metabolites analyzed in the coloured kernels, while the stronger treatment seems to drastically decrease the amounts of pigments, without changing the structure of the leftover molecules. All these findings suggest that the new colored sugary line can be considered a new functional food, able to introduce healthy compounds into the diet of many people

Characterization of "Mais delle Fiorine" (Zea mays L.) and nutritional, morphometric and genetic comparison with other maize landraces of Lombardy region (Northern Italy)

AbstractThe loss of agrobiodiversity is a topic of global impact. On a local scale, Lombardy, in the Alpine macro-Region, has lost more than 78% of its plant agrobiodiversity. Only four maize (Zea mays L. subsp. mays) landraces of Lombardy are registered in the European Register of Conservation Varieties. However, there are other maize landraces in Lombardy such as "Mais delle Fiorine", which was characterized from an agronomic, morphometric, nutritional and genetic point of view in this research and then compared with the four other landraces already registered ("Spinato di Gandino", "Rostrato Rosso di Rovetta", "Scagliolo di Carenno" and "Nero Spinoso"). "Mais delle Fiorine" resulted richer in starch (81% ± 1.6) and zinc (35.8 ± 9.1 mg Kg−1) and lower in phosphorus (3256.7 ± 204.2 mg Kg−1). The kernels in the five landraces also differ in the mean shape that is obovate without beak. A genetic distinction between "Mais delle Fiorine" and the other varieties was observed, and in particular compared to "Nero Spinoso", while "Scagliolo di Carenno" and "Rostrato Rosso di Rovetta" showed great similarities. As regards agronomical trials, "Mais delle Fiorine" can grow from the Po Valley (90 m a.s.l.) to the mountain environments of the Seriana Valley (also over 900 m a.s.l.) without significant differences in grain yield. In addition, this landrace would seem able to tolerate environments where there is a greater probability of water stress

The Potential of Low Phytic Acid1-1 Mutant in Maize (Zea mays L.): A Sustainable Solution to Non-Renewable Phosphorus

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Traditional farmers’ varieties: a valuable source of genetic variability for biofortification programs

Several studies underlined the superiority from a nutritional point of view of ancient varieties. In the last years the interest for landraces has been growing, for this reason preservation and valorisation of these genetic sources is very important. In particular these varieties are source of precious genetic variability interesting from a scientific point of view to preserve biodiversity but also for biofortification programs aimed to support small rural communities, where the particular maize germplasm has been developed. In this work we characterized from the nutritional point of view 13 ancient Italian varieties and one coming from Spain (Millo Corvo). In this pre-breeding work we demonstrate the nutritional superiority of ancient varieties if compared with modern hybrids. In particular Spinato di Gandino is the best variety for milling properties and for oil, protein, and total phosphorus content; Storo is the best variety for calorific value and for carotenoids and free phosphorus content. Using these varieties in the next future we will start a bio-fortification program aimed to obtain new populations with improved yields and high nutritional value

The Ancient Varieties of Mountain Maize: The Inheritance of the Pointed Character and Its Effect on the Natural Drying Process

The introduction of mechanized agricultural practices after the Second World War and the use of productive hybrids led to a gradual disappearance of local maize varieties. However, 13 landraces are still cultivated in North-Western Italy, in the Lombardy region; those that are cultivated in mountainous areas (roughly up to 1200 m in altitude) are often characterized by the pointed shape of their seeds (i.e., “Nero Spinoso”, “Rostrato Rosso di Rovetta”, “Spinato di Gandino” and “Scagliolo di Carenno”) and the presence of pigments (i.e., “Nero Spinoso”, “Rostrato Rosso di Rovetta”). The pointed shape of the seeds is an ancient characteristic of maize-ancestors, which negatively affects the yield by not allowing optimal “filling” of the ear. This study reports work on four different Italian varieties of pointed maize in order to assess the genetic bases of the “pointed character” and to try to explain the reasons for this adaptation to the mountain environment. The data obtained by genetic analysis, seed air-drying modeling and thermographic camera observations demonstrated that the “pointed trait” is controlled by the same genes across the different varieties studied and suggested that this peculiar shape has been selected in mountainous areas because it promotes faster drying of the seed, with the presence of pigments implementing this effect