Gene found for chloroplast movement

Inside each plant cell, light-gathering chloroplasts dance out of a cell’s shaded edges to soak up the sun or back into that shade when the light is too intense. Now a team of scientists from five Japanese research centers has found the gene that choreographs this movement, the researchers report in March 16 Science.

Chloroplasts are the powerhouses of each plant cell. They capture light energy from the sun and use it to convert carbon dioxide and water into oxygen and food. The tiny spherical or disk-shaped chloroplasts contain the pigment chlorophyll, which gives green plants their color.

When light is weak, like on a cloudy day, the chloroplasts spread across the upper faces of the cells on a leaf, giving it a deeper green color. In intense sunlight, chloroplasts retreat to the cells’ edges, making leaves look pale. Both reactions depend on the amount of blue light reaching the cells.

By noting this response in the leaves of Arabidopsis thaliana plants, Masamitsu Wada of Tokyo Metropolitan University and his colleagues identified plants with mutated copies of a gene, NPL1, that codes for a protein that detects blue light in plants and orchestrates chloroplast movement. A similar gene for blue-light detection influences how plants tip their leaves toward or away from the sun. Says Wada, “The finding of the photoreceptor means that we now know the very beginning of this phenomenon at the molecular level.”

With this knowledge, the researchers will try to determine the detailed mechanism of chloroplast movement. The newly found gene or its mutant forms could also be exploited by genetic engineers trying to elevate the efficiency of photosynthesis, Wada suggests.