Enhancing photosynthesis with sugar signals

Abstract

Improvement of photosynthetic capacity has long been a target for plant scientists. Various strategies have been employed, but in a new approach we have been testing modification of sugar signalling to improve carbon supply in plants. Sugar-signalling mechanisms enable plants to distribute resources between processes that produce, store, mobilise and consume carbon in response to changing source/ sink relationships. Trehalose metabolism has a putative carbon signalling role in microorganisms and interest in trehalose metabolism in plants has grown because the genes are now realised to be widespread in plants too. We have been testing the idea that through modification of the sugar signalling role of trehalose metabolism in plants it may be possible to improve photosynthetic performance. Expression of an E.coli transgene for trehalose phosphate synthase in Nicotiana tabacum results in enhanced photosynthetic capacity per unit leaf area. Expression of E.coli transgene for trehalose phosphate phosphatase results in decreased photosynthetic capacity per unit leaf area. These effects correlate with differences in trehalose-6-phosphate content, which through interaction with hexokinase may affect perception of carbon status as part of a signal transduction pathway altering expression of genes for photosynthesis. Enhanced photosynthetic capacity is related to increased activity of a few photosynthetic components rather than a general increase in activity of the photosynthetic apparatus. Our data support the strategy of modification of sugar signalling for increasing carbon acquisition and a role for trehalose metabolism in sugar signalling in plants.