RESUMO
A complete picture of the evolution of miRNA combinatorial regulation requires the synthesis of information on all miRNAs and their targets. MiR156 and miR529 are two combinatorial regulators of squamosa promoter binding protein-like (SBP-box) genes. Previous studies have clarified the evolutionary dynamics of their targets; however, there have been no reports on the evolutionary patterns of two miRNA regulators themselves to date. In this study, we investigated the evolutionary differences between these two miRNA families in extant land plants. Our work found that miR529 precursor, especially of its mature miRNA sequence, has a higher evolutionary rate. Such accelerating evolution of miR529 has significantly effects on its structural stability, and sequence conservation against existence of itself. By contrast, miR156 evolves more rapidly in loop region of the stable secondary structure, which may contribute to its functional diversity. Moreover, miR156 and miR529 genes have distinct rates of loss after identical duplication events. MiR529 genes have a higher average loss rate and asymmetric loss rate in duplicated gene pairs, indicating preferred miR529 gene losses become another predominant mode of inactivation, that are implicated in the contraction of this family. On the contrary, duplicated miR156 genes have a low loss rate, and could serve as another new source for functional diversity. Taken together, these results provide better insight into understanding the evolutionary divergence of miR156 and miR529 family in miRNA combinational regulation network.
Assuntos
Evolução Molecular , Regulação da Expressão Gênica de Plantas , Genes de Plantas , MicroRNAs/genética , Plantas/genética , Sequência Conservada , Deleção de Genes , Duplicação Gênica , MicroRNAs/química , Conformação de Ácido Nucleico , Oryza/genética , Precursores de RNA , Estabilidade de RNA , Análise de Sequência de DNARESUMO
Plant mechanical strength is an important agronomic trait of rice. An ethyl methane sulfonate (EMS)-induced rice mutant, fragile plant 2 (fp2), showed morphological changes and reduced mechanical strength. Genetic analysis indicated that the brittle of fp2 was controlled by a recessive gene. The fp2 gene was mapped on chromosome 10. Anatomical analyses showed that the fp2 mutation caused the reduction of cell length and cell wall thickness, increasing of cell width, and the alteration of cell wall structure as well as the vessel elements. The consequence was a global alteration in plant morphology. Chemical analyses indicated that the contents of cellulose and lignin decreased, and hemicelluloses and silicon increased in fp2. These results were different from the other mutants reported in rice. Thus, fp2 might affect the deposition and patterning of microfibrils, the biosynthesis and deposition of cell wall components, which influences the formation of primary and secondary cell walls, the thickness of cell walls, cell elongation and expansion, plant morphology and plant strength in rice.
Assuntos
Mapeamento Cromossômico , Mutação/genética , Oryza/genética , Fenômenos Biomecânicos , Parede Celular/química , Parede Celular/ultraestrutura , Segregação de Cromossomos , Cromossomos de Plantas/genética , Cruzamentos Genéticos , Genes de Plantas , Ligação Genética , Repetições Minissatélites/genética , Oryza/ultraestrutura , Fenótipo , Característica Quantitativa HerdávelRESUMO
A new double-haploid (rdh) rice plant with purple stigma and red seeds was discovered by tissue culture. Genetic analysis suggested that the trait of rdh purple stigma was controlled by a pair of dominant gene. Polymorphic analysis of microsatellite markers demonstrated that the purple stigma gene of rdh was located on rice chromosome 6 at 4.2 cM, 0.35 cM and 0.53 cM from microsatellite markers RM276, RM253 and RM111, respectively. It was believed that the purple stigma gene of rdh was the first mapped purple stigma gene on rice chromosome 6. This purple stigma gene was designated tentatively as Ps-4.
