'Cells that trigger flowering in plants identified'

Scientists have uncovered the cells in plants where a key protein triggers the flowering process.

The findings, published in the journal PNAS, may help breeders, since controlling flowering times is critical for crop development.

Until now, no one has pinpointed which cells produce the small protein, called Flowering Locus T (FT).

The study by researchers at Cornell University in the US also points to an extensive intercellular signalling system that regulates FT production.

"Understanding where FT is located and how it coordinates with other flowering factors is important to breeders; it is useful for breeders for the fine manipulation of flowering times," said Qingguo Chen, a research associate at Cornell University.

Flowering in many plants begins with the perception of day-length, which occurs in the leaves. Some plants flower in short days and others in long days.

It was previously known that in Arabidopsis plants, long day-length starts a process where leaves synthesise and transmit FT in the plant's vascular tissue, called the phloem, which carries sugars and nutrients from leaves to the rest of the plant.

FT travels to the shoot apex, the highest point of new leaves and stems, where it promotes the formation of flowers, researchers said.

Flowering regulation is complex, with the release of FT controlled by more than 30 proteins in interacting cascades.

"There's a complicated network and you can't unravel it until you realise what is going on with these particular cells, so the geography is very important," said Robert Turgeon, a professor at Cornell University.

Because leaf veins are very small and covered by photosynthetic cells rich in green chlorophyll, identifying the FT-producing cells was difficult.

In the study, Turgeon and colleagues used fluorescent proteins to identify the cells in the phloem (veins) where FT was produced.

The researchers discovered that FT was also produced in the same type of companion cells in the phloem of Maryland Mammoth tobacco.