RESUMO
Climate change could lead to an upward shift in plant distribution, exposing populations to higher levels of ultraviolet (UV)-B radiation. In the framework of an in situ strategy for conserving potato wild relatives, we evaluated the effect of high UV-B levels on natural population of Solanum kurtzianum. The hypothesis is that plants from naturally higher altitudes are more adapted to increased UV-B radiation. Two populations from low and high altitudes were field supplemented using UV-B-lamps (+UV-B) or excluded from it with plastic filters. Additionally, to assess in which extent the plant responses to these artificial experimental conditions are reproducible in natural conditions, three genotypes were cultivated in two mountain experimental gardens (EG) at different elevations. +UV-B treatment induced changes in leaf morphology and increases in phenolic compounds in both populations, indicating plant adaptation, since chlorophylls and reproductive structures were not negatively affected. These results indicate that this environmental factor may not limit the displacement of populations towards sites with higher UV-B levels. Meanwhile, in higher-altitude EG a tubers yield reduction, mainly through a decreased tuber number and a bigger accumulation of phenolic compounds than in +UV-B treatment were observed, suggesting that UV-B is not the only factor involved in plants adaptation to high altitude environments.
Assuntos
Folhas de Planta/efeitos da radiação , Tubérculos/crescimento & desenvolvimento , Sementes/fisiologia , Solanum/crescimento & desenvolvimento , Altitude , Clorofila/análise , Clorofila/metabolismo , Folhas de Planta/anatomia & histologia , Folhas de Planta/química , Tubérculos/efeitos da radiação , Sementes/efeitos da radiação , Solanum/metabolismo , Solanum/efeitos da radiação , Raios UltravioletaRESUMO
Interspecific hybridisation in tuber-bearing species of Solanum is a common phenomenon and represents an important source of variability, crucial for adaptation and speciation of potato species. In this regard, the effects of interspecific hybridisation on retrotransposon families present in the genomes, and their consequent effects on generation of genetic variability in wild tuber-bearing Solanum species, are poorly characterised. The aim of this study was to analyse the activity of retrotransposons in inter- and intraspecific hybrids between S. kurtzianum and S. microdontum, obtained by controlled crosses, and the effects on morphological, genetic and epigenetic variability. For genetic and epigenetic analysis, S-SAP (sequence-specific amplification polymorphism) and TMD (transposon methylation display) techniques were used, respectively, with specific primers for Tnt1 and Tto1 retrotransposon families (Order LTR, Superfamily Copia). The results indicate that at morphological level, interspecific hybrid genotypes differ from their parental species, whereas derived intraspecific hybrids do not. In both cases, we observed significant reductions in pollen grain viability, and a negative correlation with Tnt1 mobility. Both retrotransposons, Tto1 and Tnt1, were mobilised in the genotypes analysed, with mobility ranging from 0 to 7.8%. Furthermore, at the epigenetic level, demethylation was detected in the vicinity of Tnt1 and Tto1 in the hybrids compared with the parental genotypes. These patterns were positively correlated with the activity of the retrotransposons. The results suggest a possible mechanism through which hybridisation events generate genetic variability in tuber-bearing species of Solanum through retrotranposon activation.
Assuntos
Genoma de Planta/genética , Hibridização Genética , Retroelementos/genética , Solanum/genética , Sequência de Bases , Primers do DNA/genética , Dados de Sequência Molecular , Tubérculos/genética , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
The cultivated potato (Solanum tuberosum ssp. tuberosum) has more than 200 related wild species distributed along the Andes, adapted to a wide range of geographical and ecological areas. Since the last century, several collection expeditions were carried out to incorporate genetic variability into the potato germplasm around the world. However, little is known about the reproductive ecology and genetic population structure of natural potato population from field studies. The aim of this work is to study, in the field, the genetic variability and reproductive strategies of populations of one of the most widely distributed potato species in Argentina, Solanum kurtzianum, growing in Mendoza province. AFLP markers showed that the genetic variability is mainly present among plants within populations, indicating that in the sampled populations, sexual reproduction is more relevant than clonal multiplication (by tubers). Additional evidence was obtained evaluating the genetic diversity in populations with a distribution in patches, where several genotypes were always detected. From a field study performed in the Villavicencio Natural Reserve, we found that the average number of plump seeds per fruit was 94.3, identified and calculated the foraging distance of four insect pollinators, and demonstrated the seed dispersal by storm water channels. We argue that the breeding system, the two modes of reproduction and the ecological interaction described here may have a prominent role in determining the genetic structure of S. kurtzianum populations, and discuss the importance of field studies on population genetics, reproductive biology and ecology to design collections and conservation strategies.
Assuntos
Ecossistema , Variação Genética , Genética Populacional , Genótipo , Solanum tuberosum/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Argentina , Cruzamento , Ecologia , Tubérculos , Polinização , Reprodução , Reprodução Assexuada , Dispersão de Sementes , Sementes , Solanum tuberosum/fisiologia , ÁguaRESUMO
To investigate the molecular bases of postzygotic hybridization barriers in tuber-bearing Solanums, the wild species Solanum commersonii Dunal ex Poir. (cmm, 2n = 2x = 24, 1EBN) and Solanum acaule Bitter (acl, 2n = 4x = 48, 2EBN) were crossed in intra- and interspecific genotypic combinations, and the transcriptome of immature seeds was analyzed by using the cDNA-AFLP technique. From a total of 423 analyzed cDNA fragments, 107 (25.3%) were differentially regulated in the compatible (acl × acl and cmm × cmm) versus incompatible (acl × cmm) crosses. DNA sequence data were obtained from 21 fragments and RT-PCR analyses were carried out with five fragments to validate the cDNA-AFLP differential pattern. Sequence analysis suggested a possible role for the differentially expressed sequences in cytokinesis, cell cycle, secondary and hormonal metabolism, biodegradation, and transport. In situ hybridization experiments with fragments encoding an ubiquitin-fold modifier 1 precursor and a possible vesicle transport protein revealed expression of these genes in the embryo and endosperm. The results suggest that the collapse of the embryo and endosperm in incompatible crosses may be related to alterations in cell cycle and cytokinesis.
Assuntos
Cruzamentos Genéticos , Solanum/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Ciclo Celular , DNA Complementar/química , Genótipo , Hibridização Genética , Reação em Cadeia da Polimerase em Tempo Real , Solanum/classificação , Especificidade da EspécieRESUMO
The Endosperm Balance Number (EBN) is an important concept for potato breeding and has evolutionary importance in tuber-bearing Solanum species. The EBN is part of the post-zygotic hybridization barriers in the group and represents a reproductive isolating mechanism. Few genes have been proposed to be involved in its genetic control; until now, however, neither specific genes nor its molecular basis have been well established. Histological observations of embryo and endosperm development in inter-EBN crosses in tuber-bearing Solanum revealed phenotypes similar to those recently described in Arabidopsis seed mutants. The common feature between them is that the endosperm nuclei become greatly enlarged and that embryos are arrested at the globular stage. The proteins encoded by the Arabidopsis TITAN genes are related to chromosome dynamics and cell division. Based on the sequence of titan mutants, genes in potato species related to cell cycle and microtubule assembly were isolated. In this article a perspective model is proposed to explore the utility of Arabidopsis mutants associated with cell cycle control as a tool to elucidate the molecular basis of EBN in potato. Further research focused on the expression pattern of these genes in intra- and inter-EBN crosses in potato species will be performed.(AU)
Assuntos
Humanos , Animais , Fatores de Ribosilação do ADP/química , Arabidopsis/embriologia , Arabidopsis/genética , Arabidopsis/metabolismo , Fenótipo , Cruzamentos Genéticos , Ploidias , Solanum/embriologia , Solanum/genética , Solanum/metabolismo , Ciclo Celular , Dados de Sequência Molecular , Mutação , Proteínas de Plantas/química , Proteínas de Plantas/genética , Regulação da Expressão Gênica de Plantas , Alinhamento de SequênciaRESUMO
The Endosperm Balance Number (EBN) is an important concept for potato breeding and has evolutionary importance in tuber-bearing Solanum species. The EBN is part of the post-zygotic hybridization barriers in the group and represents a reproductive isolating mechanism. Few genes have been proposed to be involved in its genetic control; until now, however, neither specific genes nor its molecular basis have been well established. Histological observations of embryo and endosperm development in inter-EBN crosses in tuber-bearing Solanum revealed phenotypes similar to those recently described in Arabidopsis seed mutants. The common feature between them is that the endosperm nuclei become greatly enlarged and that embryos are arrested at the globular stage. The proteins encoded by the Arabidopsis TITAN genes are related to chromosome dynamics and cell division. Based on the sequence of titan mutants, genes in potato species related to cell cycle and microtubule assembly were isolated. In this article a perspective model is proposed to explore the utility of Arabidopsis mutants associated with cell cycle control as a tool to elucidate the molecular basis of EBN in potato. Further research focused on the expression pattern of these genes in intra- and inter-EBN crosses in potato species will be performed.
Assuntos
Humanos , Animais , Arabidopsis/embriologia , Arabidopsis/genética , Arabidopsis/metabolismo , Cruzamentos Genéticos , Fatores de Ribosilação do ADP/química , Fenótipo , Ploidias , Solanum/embriologia , Solanum/genética , Solanum/metabolismo , Ciclo Celular , Regulação da Expressão Gênica de Plantas , Dados de Sequência Molecular , Mutação , Proteínas de Plantas/genética , Proteínas de Plantas/química , Alinhamento de SequênciaRESUMO
The use of interspecific crosses in breeding is an important strategy in improving the genetic base of the modern cultivated potato, Solanum tuberosum L. Until now, it has normally been interspecific Solanum hybrids that have been morphologically and cytologically characterized. However, little is known about the genomic changes that may occur in the hybrid nucleus owing to the combination of genomes of different origin. We have observed novel AFLP bands in Solanum tuberosum x Solanum kurtzianum diploid hybrids; 40 novel fragments were detected out of 138 AFLP fragments analyzed. No cytological abnormalities were observed in the hybrids; however, we found DNA methylation changes that could be the cause of the observed genomic instabilities. Of 277 MSAP fragments analyzed, 14% showed methylation patterns that differed between the parental species and the hybrids. We also observed frequent methylation changes in the BC1 progeny. Variation patterns among F1 and BC1 plants suggest that some methylation changes occurred at random. The changes observed may have implications for potato breeding as an additional source of variability.
Assuntos
Genoma , Solanum tuberosum/genética , Animais , Southern Blotting , Quimera , Cruzamentos Genéticos , DNA/genética , Metilação de DNA , Genes de Plantas , Variação Genética , Polimorfismo GenéticoRESUMO
The Endosperm Balance Number (EBN) is an important concept for potato breeding and has evolutionary importance in tuber-bearing Solanum species. The EBN is part of the post-zygotic hybridization barriers in the group and represents a reproductive isolating mechanism. Few genes have been proposed to be involved in its genetic control; until now, however, neither specific genes nor its molecular basis have been well established. Histological observations of embryo and endosperm development in inter-EBN crosses in tuber-bearing Solanum revealed phenotypes similar to those recently described in Arabidopsis seed mutants. The common feature between them is that the endosperm nuclei become greatly enlarged and that embryos are arrested at the globular stage. The proteins encoded by the Arabidopsis TITAN genes are related to chromosome dynamics and cell division. Based on the sequence of titan mutants, genes in potato species related to cell cycle and microtubule assembly were isolated. In this article a perspective model is proposed to explore the utility of Arabidopsis mutants associated with cell cycle control as a tool to elucidate the molecular basis of EBN in potato. Further research focused on the expression pattern of these genes in intra- and inter-EBN crosses in potato species will be performed.
Assuntos
Arabidopsis/genética , Sementes/citologia , Solanum/genética , Fatores de Ribosilação do ADP/química , Sequência de Aminoácidos , Animais , Arabidopsis/embriologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Ciclo Celular , Núcleo Celular/metabolismo , Cruzamentos Genéticos , Regulação da Expressão Gênica de Plantas , Humanos , Dados de Sequência Molecular , Mutação , Fenótipo , Proteínas de Plantas/química , Proteínas de Plantas/genética , Ploidias , Alinhamento de Sequência , Solanum/embriologia , Solanum/metabolismoRESUMO
To understand the relationship between early seed development and the EBN (endosperm balance number) hypothesis, the embryo and endosperm growth rates in crosses among Solanum spp. with the same and different EBNs were analyzed. For the embryo, the differences in the mean cell-doubling time (MCDT) between the compatible species 2x Solanum gourlayi and Solanum acaule was 3.9 h, whereas the incompatible species Solanum commersonii had MCDT differences of 10 and 13.9 h with 2x S. gourlayi and S. acaule, respectively. The embryo growth rates of the 2EBN species S. acaule and S. gourlayi were almost twice as fast as that of the 1EBN species S. commersonii. Nuclei of variable sizes were observed in the endosperms resulting from incompatible crosses. The author discusses the possibility that the collapse of the endosperm in inter-EBN crosses could be caused by differences in the MCDT between the parents that produce hybrid endosperms with high levels of DNA synthesis and transcription activity, resulting in increased nuclear size. A model is proposed to explain the formation of enlarged endosperm nuclei in incompatible crosses in the genus Solanum.