RESUMO
Self-incompatibility (SI) of the Brassicaceae family can be overcome by CO2 gas treatment. This method has been used for decades as an effective means to obtain a large amount of inbred seeds which can then be used for F1 hybrid seed production; however, the molecular mechanism by which CO2 alters the SI pathway has not been elucidated. In this study, to obtain new insights into the mechanism of CO2-induced SI breakdown, the focus was on two inbred lines of Brassica rapa (syn. campestris) with different CO2 sensitivity. Physiological examination using X-ray microanalysis suggested that SI breakdown in the CO2-sensitive line was accompanied by a significant accumulation of calcium at the pollen-stigma interface. Pre-treatment of pollen or pistil with CO2 gas before pollination showed no effect on the SI reaction, suggesting that some physiological process after pollination is necessary for SI to be overcome. Genetic analyses using F1 progeny of a CO2-sensitive × CO2-insensitive cross suggested that CO2 sensitivity is a semi-dominant trait in these lines. Analysis of F2 progeny suggested that CO2 sensitivity could be a quantitative trait, which is controlled by more than one gene. Quantitative trait locus (QTL) analyses identified two major loci, BrSIO1 and BrSIO2, which work additively in overcoming SI during CO2 treatment. No QTL was detected at the loci previously shown to affect SI stability, suggesting that CO2 sensitivity is determined by novel genes. The QTL data presented here should be useful for determining the responsible genes, and for the marker-assisted selection of desirable parental lines with stable but CO2-sensitive SI in F1 hybrid breeding.
Assuntos
Brassica rapa/fisiologia , Dióxido de Carbono/farmacologia , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/metabolismo , Locos de Características Quantitativas/genética , Autoincompatibilidade em Angiospermas/genética , Alelos , Brassica rapa/citologia , Brassica rapa/efeitos dos fármacos , Brassica rapa/genética , Quimera , Mapeamento Cromossômico , Microanálise por Sonda Eletrônica , Flores/citologia , Flores/efeitos dos fármacos , Flores/genética , Flores/fisiologia , Ligação Genética , Genótipo , Endogamia , Fenótipo , Proteínas de Plantas/genética , Tubo Polínico/citologia , Tubo Polínico/efeitos dos fármacos , Tubo Polínico/genética , Tubo Polínico/fisiologia , Polinização , Polimorfismo Genético , Sementes/citologia , Sementes/efeitos dos fármacos , Sementes/genética , Sementes/fisiologiaRESUMO
In fast-growing Moso bamboo (Phyllostachys pubescens Mazel), cytosolic fructose 1,6-bisphosphate aldolase (aldolase; EC 4.2.2.13) was more highly active in elongating tissues than in tissues that had already finished elongating. It is well known that the removal of the culm sheath prevents bamboo from elongating. When the sheath was removed from the culm, the aldolase activity was gradually reduced over time. Two isozyme genes for aldolase, PpAldC1 and PpAldC2, were cloned from the elongating tissues of Moso bamboo. Gene expression analysis using a semi-quantitative reverse transcriptase-polymerase chain reaction revealed that PpAldC1 was highly expressed in elongating tissues but was hardly detected in elongated internodes, while PpAldC2 seemed to be expressed constitutively in both elongating and elongated tissues. Promoter analysis revealed that the expression of PpAldC1 was induced by gibberellin. These results indicated that the two genes for cytosolic aldolase in Moso bamboo showed different expression patterns and that one of them was involved in shoot elongation.
