RESUMEN
Triticale (x Triticosecale Wittmack) grains synthesize and accumulate starch as their main energy source. Starch accumulation rate and synthesis activities of ADP-glucose pyrophosphorylase, soluble starch synthases, granule-bound starch synthase and starch-branching enzyme showed similar pattern of unimodal curves during endosperm development. There was no significant difference in activity of the starch granule-bound protein isolated from total and separated starch granules at different developmental stages after anthesis in triticale. Evans Blue staining and analysis of DNA fragmentation indicated that cells of triticale endosperm undergo programmed cell death during its development. Dead cells within the endosperm were detected at 6 d post anthesis (DPA), and evidence of DNA fragmentation was first observed at 21 DPA. The period between initial detection of PCD to its rapid increase overlapped with the key stages of rapid starch accumulation during endosperm development. Cell death occurred stochastically throughout the whole endosperm, meanwhile, the activities of starch biosynthetic enzymes and the starch accumulation rate decreased in the late stages of grain filling. These results suggested that the timing and progression of PCD in triticale endosperm may interfere with starch synthesis and accumulation.
Asunto(s)
Apoptosis/fisiología , Grano Comestible/metabolismo , Endospermo/citología , Endospermo/metabolismo , Almidón/biosíntesis , Enzima Ramificadora de 1,4-alfa-Glucano/genética , Enzima Ramificadora de 1,4-alfa-Glucano/metabolismo , Amilopectina/metabolismo , Apoptosis/genética , Fragmentación del ADN , Grano Comestible/enzimología , Grano Comestible/genética , Grano Comestible/ultraestructura , Endospermo/genética , Endospermo/crecimiento & desarrollo , Endospermo/ultraestructura , Regulación de la Expresión Génica de las Plantas , Glucosa-1-Fosfato Adenililtransferasa/genética , Glucosa-1-Fosfato Adenililtransferasa/metabolismo , Microscopía Electrónica de Rastreo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Reacción en Cadena de la Polimerasa , Almidón/genética , Almidón Sintasa/genética , Almidón Sintasa/metabolismoRESUMEN
ROPs (Rho-related GTPases of plants) are small GTPases that are plant-specific signaling proteins. They act as molecular switches in a variety of developmental processes. In this study, seven cDNA clones coding for ROP GTPases have been isolated in Medicago truncatula, and conserved and divergent domains are identified in these predicted MtROP proteins. Phylogenetic analysis has indicated that MtROPs are distributed into groups II, III, IV but group I. MtROP genes are expressed in various tissues at different levels. A quantitative reverse transcription PCR analysis indicated that these MtROP genes have different expression profiles in the roots in response to infection with rhizobia. The expression of MtROP3, MtROP5 and MtROP6 are increased, as the expression of Nod factor or rhizobial-induced marker genes--NFP, Rip1 and Enod11; MtROP10 has showed enhanced expression at a certain post-inoculation time point. No significant changes in MtROP7 and MtROP9 expression have been detected and MtROP8 expression is dramatically decreased by about 80%-90%. Additionally, ROP promoter-GUS analysis has showed that MtROP3, MtROP5 and MtROP6 have elevated expression in transgenic root hairs after rhizobial inoculation. These results might suggest a role for some ROP GTPases in the regulation of early stages during rhizobial infection in symbiosis.
Asunto(s)
Proteínas de Unión al GTP/fisiología , Regulación de la Expresión Génica de las Plantas , Medicago truncatula/genética , Medicago truncatula/microbiología , Proteínas de Plantas/fisiología , Simbiosis/fisiología , Secuencia de Aminoácidos , Proteínas de Unión al GTP/química , Proteínas de Unión al GTP/genética , Regulación de la Expresión Génica de las Plantas/genética , Regulación de la Expresión Génica de las Plantas/fisiología , Datos de Secuencia Molecular , Proteínas de Plantas/química , Proteínas de Plantas/genética , Raíces de Plantas/genética , Raíces de Plantas/microbiología , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/microbiología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Rhizobium/genética , Homología de Secuencia de Aminoácido , Sinorhizobium meliloti/crecimiento & desarrollo , Sinorhizobium meliloti/fisiología , Simbiosis/genéticaRESUMEN
The effect of sowing date on grain protein, hordein fraction content and malting quality of two-rowed spring barley was investigated by using ten commercial cultivars with different grain protein content and the relationships among these traits were examined. The results showed that grain protein content and B hordein content increased as the sowing date postponed and were significantly affected by sowing date, while C and D hordein contents were less influenced by sowing date. There were significant differences in grain protein and hordein fraction content among the ten cultivars. The coefficient of variation of D hordein content was much larger than that of B and C hordein contents, suggesting its greater variation caused by different sowing dates. Beta-amylase activity and diastatic power were also significantly affected by sowing date, with malt extract being less affected. Significant differences in measured malt quality were found among the ten cultivars. Grain protein was significantly correlated with B hordein and malt extract positively and negatively, respectively. There was no significant correlation between beta-amylase activity or diastatic power and grain protein content. B hordein was negatively and significantly correlated with malt extract, but no significant correlations between C hordein, D hordein and malting quality traits.