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Biochem Biophys Res Commun. 2005 Jan 14;326(2):466-71.

Light-dependent regulation of chlorophyll b biosynthesis in chlorophyllide a oxygenase overexpressing tobacco plants.

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School of Life Sciences, Jawaharlal Nehru University, New Delhi 11067, India.


Chlorophyllide a oxygenase (CAO) that converts chlorophyllide a to chlorophyllide b was overexpressed in tobacco to increase chlorophyll (Chl) b biosynthesis and alter the Chl a/b ratio. Transgenic plants along with their wild-type cultivars were grown in low and high light intensities. In low light there was 20% increase in chlorophyll b contents in transgenic plants, which resulted in 16% reduction in the Chl a/b ratio. In high light, total Chl contents were 31% higher in transgenic plants than those of wild type. The increase in Chl a was 19% and that of Chl b was 72% leading to 31% decline of Chl a/b ratio. The increase in Chl b contents was accompanied by enhanced CAO expression that was highly pronounced in low light. As compared to low light, in high light Lhcb1 and Chl a/b transcripts abundance was significantly increased in transgenic plants suggesting a close relationship between Chl b synthesis and cab gene expression. However, there was a small increase in expression of LHCII proteins, which did not correspond to 72% increase in Chl b content in transgenic line, implying that LHCPII has the ability to bind more Chl b molecules.

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