Osmolyte-related recovery of the opaque-6 lethal phenotype in Zea mays L

Endosperm growth and development is a complex phenomenon, driven by the coordinate expression of several genes. A series of endosperm mutants with altered timing and zein synthesis rate have been studied, allowing the partial unravelling of a multifarious system, integrating carbohydrate, amino acid, and storage protein me¬tabolisms, and operating during endosperm growth and development. The exact biological function of one of these loci, the Opaque-6 (O6) gene, remains to be acknowledged. The o6 locus determines a general reduction of 19- and 22 kDa zeins as well as a number of non-zein polypeptides present in the wild type endosperm. The o6 mutants present a collapsed, dull endosperm, leaf striations and early seedling death; however, o6 seedlings can survive when grown in the presence of exogenous proline. It has been suggested that, in mutant seeds and in con¬trast with the development of the normal seeds, proline does not reach the sites of protein synthesis in adequate amounts. Yet, it has been demonstrated that amino acids other than proline are also able to restore o6 seedling le¬thality, contradicting this hypothesis. In this paper, we explored the possibility that the observed proline-mediated rescue of o6 mutant seedling lethality regarded an osmolyte-mediated mitigation of aberrant protein folding rather than the restoration of a reduced proline flux needed for protein synthesis. This hypothesis was tested by means of in vitro cultivation of o6 seedlings in the presence of putative osmolytes including a series of amino acids, me¬thylamines, and polyols. Several osmolytes were identified, which were able to restore normal growth in o6 mutant seedlings. Root reestablishment required higher osmolyte concentrations than those necessary for the recovery of the aboveground plant parts. The results presented in this paper provide sufficient preliminary evidence to assume that proline-induced recovery of the o6 mutant phenotype depends on the osmolytic properties of this amino acid

Quality related traits of the maize (Zea mays L) grain: gene identification and exploitation

Developing maize plants with improved kernel quality traits involves the ability to use existing genetic variation and to identify and manipulate commercially important genes. This will open opportunities for designing novel variation in grain composition and will provide the basis for the development of the next generation of specialty maize. This paper provides an overview of current knowledge on the identification and exploitation of genes affecting the composition, development, and structure of the maize kernel with particular emphasis on pathways relevant to endosperm growth and development, differentiation of starch-filled cells, and biosynthesis of starches, storage proteins, lipids, and carotenoids. The potential that the new technologies of cell and molecular biology will provide for the creation of new variation in the future are also indicated and discussed

The b-32 ribosome inactivating protein from maize influences fumonisin accumulation in in-vitro bioassays

Fungi of the genus Fusarium are common plant pathogens mainly associated with cereal crops. In particular, Fusarium verticillioides Sacc. is the most common toxigenic fungus in maize worldwide, causing root, stalk, and ear rot. Fusarium spp. can produce a wide range of secondary metabolites, some of which can unfavourably affect human and animal health. Owing to the potential risks of fumonisins F. verticillioides secondary metabolites, new regulations for the allowable mycotoxin limit in food and feed have been put in place by most agencies worldwide. Plants act on the attack of pathogenic fungi through a complex network of active responses such as the production of proteins toxic or inhibitory to pathogens such as RIP (Ribosome-Inactivating-Protein). The RIP present in maize endosperm (termed b-32) has been widely investigated. Similarly to other RIPs, is accumulated in the seed as an inactive pro-RIP precursor, which is converted into an active form by proteolytic processing. To understand the relationships between structure and substrate specificity of the maize b-32 RIP protein, a series of recombinant b-32 sequences, by selective deleting of different domains (RIP b-32, RIP ∆N, RIP ∆C and RIP-∆C (Ala), were prepared. Recombinant sequences were expressed in Escherichia coli to obtain high levels of recombinant proteins, which were subsequently tested for their potential ability to reduce both the colonization of F. verticillioides and fumonisin accumulation

Assesment of genetic diversity and relationships among maize inbred lines developed in Italy

The genetic diversity pattern of a sample of 144 maize inbred lines comprising 106 Italian entries, considered representative of the breeding material developed at the Bergamo Maize Breeding Station, and a sample of 38, mainly US Corn Belt based, reference lines was accessed using AFLP markers. A total of 811 polymorphic fragments were identified. Exploration of the variation disclosed by the lines by means of principal component analysis (PCA) and hierarchical clustering allowed their division into major heterotic groups. The obtained grouping of the inbred lines reflected pedigree information and resulted in the identification of major clusters derived from Lancaster Sure Crop (LSC), Iowa Stiff Stock Synthetic (BSSS), and miscellaneous heterotic breeding material. AMOVA statistics, performed on the established genetic structure, revealed a high proportion of variance between individuals and among populations stressing the high polymorphic nature of the maize pool analyzed. Regarding population structures, the genetic distance among populations (FST = 0.50 } 0.1) and the degree of inbreeding within groups (FSC = 0.46 } 0.1) did not diverge significantly, while both significantly differed from the degree of relatedness between markers within groups (FCT = 0.06 } 0.04). In conclusion, the results presented indicate that AFLPs are useful in assigning inbred lines to heterotic groups and for superior line development with the aim to maximize heterosis and consequently yield performance

The Zea mays mutants opaque-2 and opaque-7 disclose extensive changes in endosperm metabolism as revealed by protein, amino acid, and transcriptome-wide analyses

<p>Abstract</p> <p>Background</p> <p>The changes in storage reserve accumulation during maize (<it>Zea mays </it>L.) grain maturation are well established. However, the key molecular determinants controlling carbon flux to the grain and the partitioning of carbon to starch and protein are more elusive. The <it>Opaque-2 </it>(<it>O2</it>) gene, one of the best-characterized plant transcription factors, is a good example of the integration of carbohydrate, amino acid and storage protein metabolisms in maize endosperm development. Evidence also indicates that the <it>Opaque-7 </it>(<it>O7</it>) gene plays a role in affecting endosperm metabolism. The focus of this study was to assess the changes induced by the <it>o2 </it>and <it>o7 </it>mutations on maize endosperm metabolism by evaluating protein and amino acid composition and by transcriptome profiling, in order to investigate the functional interplay between these two genes in single and double mutants.</p> <p>Results</p> <p>We show that the overall amino acid composition of the mutants analyzed appeared similar. Each mutant had a high Lys and reduced Glx and Leu content with respect to wild type. Gene expression profiling, based on a unigene set composed of 7,250 ESTs, allowed us to identify a series of mutant-related down (17.1%) and up-regulated (3.2%) transcripts. Several differentially expressed ESTs homologous to genes encoding enzymes involved in amino acid synthesis, carbon metabolism (TCA cycle and glycolysis), in storage protein and starch metabolism, in gene transcription and translation processes, in signal transduction, and in protein, fatty acid, and lipid synthesis were identified. Our analyses demonstrate that the mutants investigated are pleiotropic and play a critical role in several endosperm-related metabolic processes. Pleiotropic effects were less evident in the <it>o7 </it>mutant, but severe in the <it>o2 </it>and <it>o2o7 </it>backgrounds, with large changes in gene expression patterns, affecting a broad range of kernel-expressed genes.</p> <p>Conclusion</p> <p>Although, by necessity, this paper is descriptive and more work is required to define gene functions and dissect the complex regulation of gene expression, the genes isolated and characterized to date give us an intriguing insight into the mechanisms underlying endosperm metabolism.</p

Cloning and Characterization of GLOSSY1, a Maize Gene Involved in Cuticle Membrane and Wax Production

The cuticle covering the aerial organs of land plants plays a protective role against several biotic and abiotic stresses and, in addition, participates in a variety of plant-insect interactions. Here, we describe the molecular cloning and characterization of the maize (Zea mays) GLOSSY1 (GL1) gene, a component of the pathway leading to cuticular wax biosynthesis in seedling leaves. The genomic and cDNA sequences we isolated differ significantly in length and in most of the coding region from those previously identified. The predicted GL1 protein includes three histidine-rich domains, the landmark of a family of membrane-bound desaturases/hydroxylases, including fatty acid-modifying enzymes. GL1 expression is not restricted to the juvenile developmental stage of the maize plant, pointing to a broader function of the gene product than anticipated on the basis of the mutant phenotype. Indeed, in addition to affecting cuticular wax biosynthesis, gl1 mutations have a pleiotropic effect on epidermis development, altering trichome size and impairing cutin structure. Of the many wax biosynthetic genes identified so far, only a few from Arabidopsis (Arabidopsis thaliana) were found to be essential for normal cutin formation. Among these is WAX2, which shares 62% identity with GL1 at the protein level. In wax2-defective plants, cutin alterations induce postgenital organ fusion. This trait is not displayed by gl1 mutants, suggesting a different role of the maize and Arabidopsis cuticle in plant development

Maize Histone Deacetylase hda101 Is Involved in Plant Development, Gene Transcription, and Sequence-Specific Modulation of Histone Modification of Genes and Repeats[W]

Enzymes catalyzing histone acetylation and deacetylation contribute to the modulation of chromatin structure, thus playing an important role in regulating gene and genome activity. We showed that downregulation and overexpression of the maize (Zea mays) Rpd3-type hda101 histone deacetylase gene induced morphological and developmental defects. Total levels of acetylated histones and histone acetylation of both repetitive and nonrepetitive sequences were affected in hda101 transgenic mutants. However, only transcript levels of genes but not repeats were altered. In particular, hda101 transgenic mutants showed differential expression of genes involved in vegetative-to-reproductive transition, such as liguleless2 and knotted-like genes and their repressor rough sheath2, which are required for meristem initiation and maintenance. Perturbation of hda101 expression also affected histone modifications other than acetylation, including histone H3 dimethylation at Lys-4 and Lys-9 and phosphorylation at Ser-10. Our results indicate that hda101 affects gene transcription and provide evidence of its involvement in setting the histone code, thus mediating developmental programs. Possible functional differences between maize hda101 and its Arabidopsis thaliana ortholog HDA19 are discussed

Mitochondrial ribosomal proteins involved in tellurite resistance in yeast Saccharomyces cerevisiae

none11noA considerable body of evidence links together mitochondrial dysfunctions, toxic action of metalloid oxyanions, and system and neurodegenerative disorders. In this study we have used the model yeast Saccharomyces cerevisiae to investigate the genetic determinants associated with tellurite resistance/sensitivity. Nitrosoguanidine-induced K2TeO3-resistant mutants were isolated, and one of these mutants, named Sc57-Te5 R, was characterized. Both random spore analysis and tetrad analysis and growth of heterozygous (TeS/Te5 R) diploid from Sc57-Te5 R mutant revealed that nuclear and recessive mutation(s) was responsible for the resistance. To get insight into the mechanisms responsible for K2TeO3-resistance, RNA microarray analyses were performed with K2TeO3-treated and untreated Sc57-Te5 R cells. A total of 372 differentially expressed loci were identified corresponding to 6.37% of the S. cerevisiae transcriptome. Of these, 288 transcripts were up-regulated upon K2TeO3 treatment. About half of up-regulated transcripts were associated with the following molecular functions: oxidoreductase activity, structural constituent of cell wall, transporter activity. Comparative whole-genome sequencing allowed us to identify nucleotide variants distinguishing Sc57-Te5 R from parental strain Sc57. We detected 15 CDS-inactivating mutations, and found that 3 of them affected genes coding mitochondrial ribosomal proteins (MRPL44 and NAM9) and mitochondrial ribosomal biogenesis (GEP3) pointing out to alteration of mitochondrial ribosome as main determinant of tellurite resistance.openPontieri, Paola; Hartings, Hans; Di Salvo, Marco; Massardo, Domenica R.; De Stefano, Mario; Pizzolante, Graziano; Romano, Roberta; Troisi, Jacopo; Del Giudice, Angelica; Alifano, Pietro; Del Giudice, Luigi*Pontieri, Paola; Hartings, Hans; Di Salvo, Marco; Massardo, Domenica R.; De Stefano, Mario; Pizzolante, Graziano; Romano, Roberta; Troisi, Jacopo; Del Giudice, Angelica; Alifano, Pietro; Del Giudice, Luig