RESUMEN
The processes that contribute to plant organ morphogenesis are spatial-temporally organized. Within the meristem, mitosis produces new cells that subsequently engage in cell expansion and differentiation programs. The latter is frequently accompanied by endoreplication, being an alternative cell cycle that replicates the DNA without nuclear division, causing a stepwise increase in somatic ploidy. Here, we show that the Arabidopsis SCL28 transcription factor promotes organ growth by modulating cell expansion dynamics in both root and leaf cells. Gene expression studies indicated that SCL28 regulates members of the SIAMESE/SIAMESE-RELATED (SIM/SMR) family, encoding cyclin-dependent kinase inhibitors with a role in promoting mitotic cell cycle (MCC) exit and endoreplication, both in response to developmental and environmental cues. Consistent with this role, mutants in SCL28 displayed reduced endoreplication, both in roots and leaves. We also found evidence indicating that SCL28 co-expresses with and regulates genes related to the biogenesis, assembly, and remodeling of the cytoskeleton and cell wall. Our results suggest that SCL28 controls, not only cell proliferation as reported previously but also cell expansion and differentiation by promoting MCC exit and endoreplication and by modulating aspects of the biogenesis, assembly, and remodeling of the cytoskeleton and cell wall.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Proliferación Celular , Endorreduplicación , Regulación de la Expresión Génica de las Plantas , MitosisRESUMEN
Chromatin assembly factor-1 (CAF-1) is a histone H3/H4 chaperone that participates in DNA and chromatin interaction processes. In this manuscript, we show that organs from CAF-1 deficient plants respond differently to ultraviolet-B (UV-B) radiation than to other genotoxic stresses. For example, CAF-1 deficient leaves tolerate better UV-B radiation, showing lower cyclobutane pyrimidine dimer (CPD) accumulation, lower inhibition of cell proliferation, increased cell wall thickness, UV-B absorbing compounds, and ploidy levels, whereas previous data from different groups have shown that CAF-1 mutants show shortening of telomeres, loss of 45S rDNA, and increased homologous recombination, phenotypes associated to DNA breaks. Interestingly, CAF-1 deficient roots show increased inhibition of primary root elongation, with decreased meristem size due to a higher inhibition of cell proliferation after UV-B exposure. The decrease in root meristem size in CAF-1 mutants is a consequence of defects in programmed cell death after UV-B exposure. Together, we provide evidence demonstrating that root and shoot meristematic cells may have distinct protection mechanisms against CPD accumulation by UV-B, which may be linked with different functions of the CAF-1 complex in these different organs.
Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/efectos de la radiación , Daño del ADN , Hojas de la Planta/efectos de la radiación , Raíces de Plantas/efectos de la radiación , Factores de Empalme de ARN/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Proliferación Celular , Pared Celular/metabolismo , Endorreduplicación , Pigmentos Biológicos/metabolismo , Hojas de la Planta/metabolismo , Raíces de Plantas/metabolismo , Rayos UltravioletaRESUMEN
Cultivated potatoes (Solanum tuberosum L.), domesticated from wild Solanum species native to the Andes of southern Peru, possess a diverse gene pool representing more than 100 tuber-bearing relatives (Solanum section Petota). A diversity panel of wild species, landraces, and cultivars was sequenced to assess genetic variation within tuber-bearing Solanum and the impact of domestication on genome diversity and identify key loci selected for cultivation in North and South America. Sequence diversity of diploid and tetraploid Stuberosum exceeded any crop resequencing study to date, in part due to expanded wild introgressions following polyploidy that captured alleles outside of their geographic origin. We identified 2,622 genes as under selection, with only 14-16% shared by North American and Andean cultivars, showing that a limited gene set drove early improvement of cultivated potato, while adaptation of upland (Stuberosum group Andigena) and lowland (S. tuberosum groups Chilotanum and Tuberosum) populations targeted distinct loci. Signatures of selection were uncovered in genes controlling carbohydrate metabolism, glycoalkaloid biosynthesis, the shikimate pathway, the cell cycle, and circadian rhythm. Reduced sexual fertility that accompanied the shift to asexual reproduction in cultivars was reflected by signatures of selection in genes regulating pollen development/gametogenesis. Exploration of haplotype diversity at potato's maturity locus (StCDF1) revealed introgression of truncated alleles from wild species, particularly Smicrodontum in long-day-adapted cultivars. This study uncovers a historic role of wild Solanum species in the diversification of long-day-adapted tetraploid potatoes, showing that extant natural populations represent an essential source of untapped adaptive potential.
Asunto(s)
Evolución Biológica , Domesticación , Genes de Plantas/genética , Variación Genética , Tubérculos de la Planta/genética , Solanum tuberosum/genética , Solanum/genética , Alelos , Metabolismo de los Hidratos de Carbono/genética , Ciclo Celular/genética , Cromosomas de las Plantas , Ritmo Circadiano/genética , Diploidia , Endorreduplicación/genética , Fertilidad/genética , Gametogénesis/genética , Regulación de la Expresión Génica de las Plantas , Pool de Genes , Genotipo , Haplotipos , Redes y Vías Metabólicas/genética , América del Norte , Perú , Fenotipo , Filogenia , Polen/genética , Polen/crecimiento & desarrollo , Poliploidía , América del Sur , Especificidad de la Especie , TetraploidíaRESUMEN
A micropropagação facilita a obtenção de mudas de mudas de pitaya, Hylocereus undatus Haw; porém, pode propiciar alterações genéticas, como a polissomatia, endopoliploidia ou endorreduplicação. Neste trabalho, objetivou-se desenvolver protocolo para micropropagação e verificar a endorreduplicação em pitaya vermelha. Cladódios de pitaya foram micropropagados em meio de cultura MS, com 0,1 mg L-1 de ANA, acrescido de BAP e cinetina, nas dosagens 0, 1, 5 e 10 mg L-1, sendo o meio MS sem reguladores de crescimento utilizado como tratamento controle. O delineamento experimental utilizado foi inteiramente casualizado em fatorial 2x8 (ausência e presença de luz e 8 diferentes meios de cultura), totalizando 16 tratamentos, sendo 4 repetições de 3 explantes. O experimento foi conduzido na presença e ausência de luz em sala de crescimento a 25 ± 2ºC, irradiância média de 42 W m-2 e fotoperíodo de 16 horas, por 120 dias. A análise de citometria de fluxo foi utilizada em 3 explantes por tratamento. Amostras de cladódios, juntamente com o padrão interno (ervilha) foram triturados com 1 mL de tampão de extração LB01 e 25 mL de iodeto de propídeo, analisados em citômetro de fluxo. Os explantes submetidos à ausência de luz não responderam aos tratamentos. O meio de cultura que proporciona melhor crescimento e desenvolvimento in vitro é o MS acrescido de 0,1 mg L-1 de ANA e BAP ou cinetina nas concentrações de 1 ou 5 mg L-1. O meio de cultura que proporciona aos explantes maior variação na quantidade de DNA é MS com 10 mg L-1 de BAP e 0,1 mg L-1 de ANA. O fenômeno da endorreduplicação é observado em todos os tratamentos analisados.
Micropropagation makes the obtaining of seedlings of red pitaya easier, but, it can cause genetic mutations such as polysomaty, endopolyploidy or endoreduplication. In this work, it was aimed to develop a protocol for micropropagation and check the endoreduplication in red pitaya. Pitaya cladodes were micropropagated im MS culture medium with 0.1 mg L-1 of ANA added of BAP and kinetin at the dosages of 0, 1, 5 and 10 mg L-1, the MS medium without any growth regulators being used as the control treatment. The experimental design utilized was the completely randomized in factorial 2 x 8 (absence and presence of light and 8 different culture media), amounting to 16 treatments, namely, 4 replications of 3 explants. The experiment was conducted in the presence and absence of light in a growth room at 25 ± 2 ºC, average irradiance of 42W m-2 and photoperiod of 16 hours for 120 days. The flow cytometry analysis was utilized on three explants per treatment. Cladode samples, along with the internal pattern (pea) were ground with 1 ml of extraction buffer LB 01 and 25 mL of propide iodide, analyzed in flow cytometer. The explants submitted to the absence of light did not respond to the treatments. The culture medium which brings about the best in vitro growth and development is the MS added of 0.1 mg L-1 of ANA and BAP or kinetin at the concentrations of 1 or 0.5 mg L-1. The culture medium which provides to the explants greatest variation in the amount of DNA is MS with 10 mg L-1 of BAP and 0.1 mg L-1 of ANA. The phenomenon of endoreduplication is found in all the treatments investigated.