How fungi recognize (and infect) plants | Mennat El Ghalid

"Will the blight end the chestnut?

The farmers rather guess not.

It keeps smouldering at the roots

And sending up new shoots

Till another parasite

Shall come to end the blight."

At the beginning of the 20th century,

the eastern American chestnut population, counting nearly four billion trees,

was completely decimated by a fungal infection.

Fungi are the most destructive pathogens of plants,

including crops of major economic importance.

Can you imagine that today,

crop losses associated with fungal infection

are estimated at billions of dollars per year, worldwide?

That represents enough food calories to feed half a billion people.

And this leads to severe repercussions,

including episodes of famine in developing countries,

large reduction of income for farmers and distributors,

high prices for consumers

and risk of exposure to mycotoxin, poison produced by fungi.

The problems that we face

is that the current method used to prevent and treat

those dreadful diseases,

such as genetic control, exploiting natural sources of resistance,

crop rotation or seed treatment, among others,

are still limited or ephemeral.

They have to be constantly renewed.

Therefore, we urgently need to develop more efficient strategies

and for this, research is required to identify biological mechanisms

that can be targeted by novel antifungal treatments.

One feature of fungi is that they cannot move

and only grow by extension to form a sophisticated network,

the mycelium.

In 1884, Anton de Bary, the father of plant pathology,

was the first to presume that fungi are guided by signals

sent out from the host plant,

meaning a plant upon which it can lodge and subsist,

so signals act as a lighthouse

for fungi to locate, grow toward, reach

and finally invade and colonize a plant.

He knew that the identification of such signals

would unlock a great knowledge that then serves to elaborate strategy

to block the interaction between the fungus and the plant.

However, the lack of an appropriate method at that moment

prevented him from identifying this mechanism at the molecular level.

Using purification and mutational genomic approaches,

as well as a technique

allowing the measurement of directed hyphal growth,

today I'm glad to tell you that after 130 years,

my former team and I could finally identify such plant signals

by studying the interaction between a pathogenic fungus

called Fusarium oxysporum

and one of its host plants, the tomato plant.

As well, we could characterize

the fungal receptor receiving those signals

and part of the underlying reaction occurring within the fungus

and leading to its direct growth toward the plant.

(Applause)

Thank you.

(Applause)

The understanding of such molecular processes

offers a panel of potential molecules

that can be used to create novel antifungal treatments.

And those treatments would disrupt

the interaction between the fungus and the plant

either by blocking the plant signal

or the fungal reception system which receives those signals.

Fungal infections have devastated agriculture crops.

Moreover, we are now in an era

where the demand of crop production is increasing significantly.

And this is due to population growth, economic development,

climate change and demand for bio fuels.

Our understanding of the molecular mechanism

of interaction between a fungus and its host plant,

such as the tomato plant,

potentially represents a major step towards developing more efficient strategy

to combat plant fungal diseases

and therefore solving of problems that affect people's lives,

food security and economic growth.

Thank you.

(Applause)