Scientists have solved a long-standing mystery of how plants respond to elevated CO2 levels, a discovery that could help engineer crops that can deal with droughts and high temperatures.
Biologists at The University California, San Diego found out how plants reduce the numbers of their breathing pores in response to rising carbon dioxide levels in the atmosphere.
They discovered a new genetic pathway in plants, made up of four genes from three different gene families that control the density of breathing pores - or "stomata" - in plant leaves in response to elevated CO2 levels.
Their discovery could help biologists better understand how the steadily increasing levels of CO2 in our atmosphere are affecting the ability of plants and economically important crops to deal with heat stress and drought.
"Because elevated CO2 reduces the density of stomatal pores in leaves, this is, at first sight beneficial for plants as they would lose less water," said Julian Schroeder, who headed the research.
"However, the reduction in the numbers of stomatal pores decreases the ability of plants to cool their leaves during a heat wave via water evaporation. Less evaporation adds to heat stress in plants, which ultimately affects crop yield," said Schroeder.
Working in a tiny mustard plant called Arabidopsis, which is used as a genetic model and shares many of the same genes as other plants and crops, Schroeder and his team discovered that the proteins encoded by the four genes they discovered repress the development of stomata at elevated CO2 levels.
Using a combination of systems biology and bioinformatic techniques, the scientists cleverly isolated proteins, which, when mutated, abolished the plant's ability to respond to CO2 stress.
Cawas Engineer, the first author of the study, found that when plants sense atmospheric CO2 levels rising, they increase their expression of a key peptide hormone called Epidermal Patterning Factor-2, EPF2.
"The EPF2 peptide acts like a morphogen which alters stem cell character in the epidermis of growing leaves and blocks the formation of stomata at elevated CO2," said Engineer.
"Such a 'sensing and response' mechanism involving CRSP and EPF2 could be used to engineer crop varieties which are better able to perform in the current and future high CO2 global climate where fresh water availability for agriculture is dwindling," said Engineer.
The research was published in the journal Nature.
