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Abstract  We analyzed the impact of ethylene and auxin disturbances on callus, shoots and Agrobacterium rhizogenes-induced hairy root formation in tomato (Solanum lycopersicum L.). The auxin low-sensitivity dgt mutation showed little hairy root initiation, whereas the ethylene low-sensitivity Nr mutation did not differ from the control Micro-Tom cultivar. Micro-Tom and dgt hairy roots containing auxin sensitivity/biosynthesis rol and aux genes formed prominent callus onto media supplemented with cytokinin. Under the same conditions, Nr hairy roots did not form callus. Double mutants combining Rg1, a mutation conferring elevated shoot formation capacity, with either dgt or Nr produced explants that formed shoots with little callus proliferation. The presence of rol  aux genes in Rg1 hairy roots prevented shoot formation. Taken together, the results suggest that although ethylene does not affect hairy root induction, as auxin does, it may be necessary for auxin-induced callus formation in tomato. Moreover, excess auxin prevents shoot formation in Rg1. [ABSTRACT FROM AUTHOR]

Abstract??Sugarcane (Saccharumspp.) is a highly efficient biomass and sugar producing crop. Leaf reactions have been considered as potential rate-limiting step for sucrose accumulation in sugarcane stalks. To characterize the sugarcane leaf transcriptome, field-grown mature leaves from cultivar ?SP80-3280? were analyzed using Serial Analysis of Gene Expression (SAGE). From 480 sequenced clones, 9,482 valid tags were extracted, with 5,227 unique sequences, from which 3,659 (70%) matched at least a sugarcane assembled sequence (SAS) with putative function; while 872 tags (16.7%) matched SAS with unknown function; 523 (10%) matched SAS without a putative annotation; and only 173 (3.3%) did not match any sugarcane ESTs. Based on gene ontology (GO), photosystem (PS) I reaction center was identified as the most frequent gene product location, followed by the remaining sites of PS I, PS II and thylakoid complexes. For metabolic processes, photosynthesis light harvesting complexes; carbon fixation; and chlorophyll biosynthesis were the most enriched GO-terms. Considering the alternative photosynthetic C4cycles, tag frequencies related to phosphoenolpyruvate carboxykinase (PEPCK) and aspartate aminotransferase compared to those for NADP+-malic enzyme (NADP-ME) and NADP-malate dehydrogenase, suggested that PEPCK-type decarboxylation appeared to predominate over NADP-ME in mature leaves, although both may occur, opposite to currently assumed in sugarcane. From the unique tag set, 894 tags (17.1%) were assigned as potentially derived from antisense transcripts, while 73 tags (1.4%) were assigned to more than one SAS, suggesting the occurrence of alternative processing. The occurrence of antisense was validated by quantitative reverse transcription amplification. Sugarcane leaf transcriptome provided new insights for functional studies associated with sucrose synthesis and accumulation. [ABSTRACT FROM AUTHOR]

A sample of 94 accessions of Theobroma cacao L. (cacao), representing four populations from the Brazilian Amazon (Acre, Rondônia, lower Amazon and upper Amazon) were analyzed using microsatellite markers to assess the genetic diversity and the natural population structure. From the 19 microsatellite loci tested, 11 amplified scorable products, revealing a total of 49 alleles, including two monomorphic loci. The Brazilian upper Amazon population contained the largest genetic diversity, with the most polymorphic loci, the highest observed heterozygosity; and the majority of rare alleles, thereby this region might be considered part of the center of diversity of the species. The observed heterozygosity for all the Brazilian populations (Ho = 0.347) was comparable with values reported for other similar upper Amazon Forastero cacao populations, with the Acre and Rondônia displaying the lowest values. The lower Amazon population, traditionally defined as highly homozygous, presented an unexpectedly high observed heterozygosity (Ho = 0.372), disclosing rare and distinct alleles, with large identity with the upper Amazon population. It was hypothesized that part of the lower Amazon population might derive from successive natural or intentional introduction of planting material from other provenances, mainly upper Amazon. Most of the loci exhibited a lower observed heterozygosity than expected, suggesting that self-pollination might be more common than usually assumed in cacao, but excess of homozygotes might also derive from sub-grouping (Wahlund effect) or from sampling related individuals. Most of the gene diversity was found to occur within groups, with small differentiation between the four Brazilian Amazon populations, typical of species with high gene flow. [ABSTRACT FROM AUTHOR]

Banana (Musa spp.) is one of the most consumed fruits worldwide. Production is based mainly on triploid cultivars, and most genetic improvement programs aim to generate tetraploid hybrids obtained from the crossing of established triploid cultivars with a diploid parent genotype, improved or wild, exhibiting the trait of interest, normally resistance to biotic factors. Microsatellites were used to investigate the genetic variability and relationships between 58 Musa genotypes, including 49 diploids and nine triploid cultivars maintained at the Musa germplasm collection of the Brazilian dessert banana breeding program. Thirty-three primer pairs developed for banana were tested, and nine amplified reproducible and discrete fragments, producing a total of 115 alleles. The average number of alleles amplified per primer was 12.8, ranging from 10 to 15. The diploid genotypes presented the largest genetic variability, demonstrated by the large number of alleles detected, and the low similarity between the clones. The phenetic analysis clustered the triploid cultivars in a separated group, with the exception of the ‘Nanica’ and ‘Gros Michel’ cultivars, which showed high similarity with the diploid cultivar ‘Mambee Thu’. It was not possible to separate the wild diploid genotypes from the cultivated ones, indicating a common origin of these genotypes. A high proportion of duplicated alleles and/or loci was observed for diploid and triploid genotypes. The information gathered about the similarity between diploid and triploid accessions will help to define potential crosses to maximize the recovery of the typical fruit qualities required in Brazil (AAB, Pome and Silk dessert banana). [ABSTRACT FROM AUTHOR]