花怎么知道什么時候該開？

Researchers have uncovered exactly where a key protein forms before it triggers the flowering process in plants.Until now, no one has pinpointed which cells produce the small protein, called Flowering Locus T (FT).The study also points to an extensive intercellular signaling system that regulates FT production.

在植物中，F(xiàn)lowering Locus T(FT)是一種關(guān)鍵蛋白質(zhì)，它的形成會觸發(fā)開花過程。最近，研究人員發(fā)現(xiàn)了FT的準確形成位置，以及調(diào)控FT分泌的大規(guī)模細胞間信號系統(tǒng)。在此之前，沒有人知道它到底由哪些細胞分泌。

"Understanding where FT is located and how it coordinates with other flowering factors is important to breeders; it's useful for breeders for the fine manipulation of flowering times," says Qingguo Chen, the paper's first author and a research associate in the lab of Robert Turgeon, the paper's senior author and professor of plant biology at Cornell University.

本研究由康奈爾大學(xué)植物學(xué)教授Robert Turgeon(資深作者)和實驗室研究助理Qingguo Chen(第一作者)共同完成。Qingguo Chen表示：對培植者來說，了解FT的位置以及它如何和其它開花因素協(xié)同作用很重要;他們能夠以此精細控制植物的開花時間。

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.

許多植物的開花過程始于葉子對白晝長度的感知。有些植物在晝短的日子里開花，有些植物在晝長的日子里開花。

It was previously known that in Arabidopsis plants, long day-length starts a process where leaves synthesize 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.

科學(xué)家早就知道，在擬南芥這種植物中，長晝會使葉子合成FT，并并通過韌皮部進行運輸——韌皮部負責(zé)將糖分和營養(yǎng)物質(zhì)從葉子運輸?shù)狡渌参锊课?

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

FT來到枝條尖，即新莖葉的最高點，并在那里觸發(fā)開花過程。

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

開花過程的調(diào)控非常復(fù)雜，F(xiàn)T的釋放由30多種蛋白質(zhì)控制。

"There's a complicated network and you can't unravel it until you realize what is going on with these particular cells, so the geography is very important," says Turgeon.

它們相互作用，形成復(fù)雜網(wǎng)絡(luò)。只有確切了解這些特定細胞所發(fā)生的事情，才能夠解釋整個過程。所以，“(細胞)地理”很重要。

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

由于葉脈非常小，又被大量富含葉綠素的光合細胞所覆蓋;因此，識別分泌FT的細胞非常困難。

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

這回，研究人員采用熒光蛋白，識別出韌皮部(葉脈)里分泌FT的細胞。

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

他們發(fā)現(xiàn)，在馬里蘭猛犸煙草的韌皮部中，一種同類型的伴細胞也會分泌FT。

Furthermore, when they killed these companion cells, it delayed flowering in both Arabidopisis and the tobacco plants.

當(dāng)研究人員破壞這些伴細胞時，擬南芥和馬里蘭猛犸的開花過程都推遲了。

When they looked more closely at the pathways that lead to flowering, they found that killing these companion cells stopped the process downstream of FT, but not upstream, confirming that FT originates in these cells and that the synthesis of FT is regulated by an extensive intercellular signaling system.

當(dāng)他們仔細觀察開花通道時，發(fā)現(xiàn)破壞伴細胞會終止FT的下游過程，但不終止它的上游過程。這證明FT發(fā)源于這些細胞，而FT的合成受到大規(guī)模細胞間信號系統(tǒng)的調(diào)控。