Science offers new insights into how plants rely on calcium waves to respond systematically to injury and other stresses

Long-standing theories about how plants rely on calcium waves to respond systematically to injury and other stresses have been given new perspectives
.

Researchers at the John Innes Center have shown that calcium waves are not a primary response, but a secondary response
to waves of amino acids released from wounds.

These findings challenge the inherent understanding
of the long-distance transmission of plant signaling molecules and the mechanisms by which information is transmitted from stress points through living and non-living plant tissues.

Over the years, injuries and other trauma have been observed to trigger calcium waves that travel short distances from cell to cell and long distances from leaf to leaf
.

These calcium waves are reminiscent of mammalian nerve signals, but since the plant has no nerve cells, the mechanism of this process has been questionable
.

When a cell is injured, it releases a wave of glutamate, an amino acid
.
As this wave travels through plant tissue, it activates calcium channels
in the cell membrane that passes through.
This activation looks like a calcium wave, but is a passive response, or a "readout"
that moves the glutamate signal.

Previous hypotheses explaining how calcium waves pass through plant cells involve the active mechanism
of calcium signaling propagation.
These hypotheses rely on signals traveling along cell membranes, or through pressure waves in the xylem, but do not explain how this response is passed from one cell to the next
.

Dr Christine Faulkner, group leader at the John Innes Center, said: "Every time I propose an active propagation model, I question how this wave propagates from cell to cell
.
In my opinion, there is a hole in this theory, and this study reveals a new mechanism that suggests that calcium waves are not what
it seems.
”

Dr.
Faulkner's research group specializes in intercellular filaments, which are channels or bridges
that connect cells.
The team speculated that trauma signals are transmitted from one cell to another via intercellular filaments
.
However, by using quantitative imaging techniques, data modeling, and genetics, they found that the moving signal is a glutamate wave that travels
outside the cell along the cell wall.

Glutamate and calcium waves are interconnected – glutamate triggers a calcium response
.
You can think of it as a corridor
.
Glutamate rushed down the hallway, and as it passed a door, it kicked
it open.
The reaction of calcium is the opening
of the door.
Until now, it had been thought that what moved along the corridor was hydraulics or a series of propagating chemical reactions, but our research shows that this is not the
case.
Dr.
Faulkner said
.

Dr Analisa Berandi, first author of the study, said: "We have demonstrated that calcium waves are synchronized with glutamate waves and that their dynamics match
diffusion and flow transport.
This research makes us rethink what
we know.
I hope that our research will spark debate and give a new perspective
on data that has been in this field for a long time.
”

The diffusion and volumetric flow of amino acids mediated by calcium waves in plants appears in Science Advances
.