Springtime for wheat starts with a gene that ‘sees’ light

Scientists from the University of California, Davis, (UC Davis) have discovered the function of a gene that allows wheat to discern the length of each day and night. When they knocked out the gene, wheat flowering was delayed for more than 100 days.

The finding, reported in the current edition of the Proceedings of the National Academy of Sciences, gives plant breeders and researchers a new tool for either accelerating or delaying wheat's flowering time, which is important for adapting the crop to new and changing climates.

Though plants don't have the sensory organs to actually see light, they have developed biochemical responses for detecting when it is springtime.  Proteins called phytochromes are activated by red light and regulate the responses of many other genes.

The UC Davis researchers found that the gene -- named Phytochrome C -- changes form when it detects the red hues of daylight and activates a separate gene, known as Photoperiod 1.  This gene is also regulated by the circadian clock that oscillates with every 24-hour period. The simultaneous regulation of Photoperiod 1 by light signal (an external signal) and by the circadian clock (an internal oscillator) is required to measure the length of days and nights.

The discovery of the Phytochrome C function was made possible by a genetic technique called ''TILLING,'' (Targeting Induced Local Lesions IN Genomes).

The process was developed by UC Davis plant biology professor Luca Comai and adapted to wheat by UC Davis plant sciences professor Jorge Dubcovsky, a wheat geneticist and senior author on the new paper.

TILLING allows the researchers to make almost any gene inoperative. In this study, they were able to knock out the different copies of Phytochrome C in order to study their function.

''We've invested a lot of our time in recent years to develop a TILLING resource for wheat,'' Dubcovsky said. ''That has enabled us to do studies in wheat that we were not able to do in the past. We couldn't answer those questions before.''

While breeders are already able to modify flowering time in wheat, this discovery provides one more way of doing that. The scientists will now start looking for variations in Phytochrome C that can be used to alter the flowering time in wheat. This would allow breeders to adapt wheat to new geographic climates and would mean farmers in northern regions could better manage their shorter growing seasons.

''We've gone one step deeper in our basic understanding of wheat flowering,'' Dubcovsky said.