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The chloroplast genome and chloroplast gene expression

Published on May 31, 2022   50 min

A selection of talks on Plant & Animal Sciences

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0:00
I'm Professor Christopher Howe from the Department of Biochemistry at the University of Cambridge in the United Kingdom I'm going to talk about the chloroplast genome and chloroplast gene expression.
0:14
We'll look, first, at the experiments that led to the recognition that the chloroplast has its own genome and genetic system. We'll then look at the organisation and content of the chloroplast genome. We'll look at the expression of the chloroplast genome. Finally, we'll consider why there should be a separate genome in the chloroplast at all.
0:38
The first experimental observations that ultimately were interpreted as indicating the presence of a chloroplast genome, were reported early in the 20th Century in two classic papers by Carl Correns and Erwin Baur. Those papers looked at the inheritance of variegation in plants that included Mirabilis, which is also known as the 4:00 o'clock plant, and Pelargonium, the geranium. Although some instances of variegation in plants were found to be inherited according to classic Mendelian principles, this wasn't always the case. In these exceptions, the results of a cross were found to depend on the maternal, that's to say the female parent, the parent that produced the egg, and not the pollen. This phenomenon was termed a reciprocal cross effect.
1:33
Correns showed with variegated Mirabilis, that when green shoots, as the female parent, were pollinated with pollen from a white plant, as the male parent, the progeny were always green. When the reciprocal cross was performed, then the results were different. With the reciprocal cross, when white shoots were pollinated with pollen from a green plant, the resulting progeny were white. Now, with conventional Mendelian inheritance, the results of the cross should be independent of which parent is male and which is female. The pattern observed with the maternal parent alone determining the outcome of the cross was referred to as maternal, or sometimes uniparental-maternal, inheritance. With Pelargonium, the results were a bit more complicated, with both parents in principle able to contribute to the results of a cross, but again not according to a recognised standard Mendelian pattern. In that case, it is referred to as bi-parental inheritance. These results have been extended to a wide range of other plant species and we now recognise maternal, bi-parental, and paternal inheritance patterns. We understand these patterns as being
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The chloroplast genome and chloroplast gene expression

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