Hair-Like Structures On Leaves Activate Immune System Of Plants During Rain: Study
When plants are exposed to rain, hair-like structures on the leaf structure called trichomes recognise rain as a risk factor for causing infections.
New Delhi: All plants need rain to survive because it is the source of water required by them to perform photosynthesis. However, rain also contains bacteria and other pathogens which can be harmful to plants.
Therefore, a question arises: how do planets evade the threat from pathogens.
Researchers at the Nagoya University in Japan recently conducted a study, in which they have revealed that when plants are exposed to rain, hair-like structures on the leaf structure called trichomes recognise rain as a risk factor for causing infections. As a result, the trichomes activate the plants' immune system to prevent infections.
The findings of the study were recently published in the journal Nature Communications, and could contribute to the development of methods to protect plants from infectious diseases caused by rain, according to the researchers.
How Do Plants Activate Their Immune System?
Just like humans, and other multicellular organisms, plants have their own immune system. Upon detecting pathogens, plants express immune-related genes to prevent themselves from being infected.
Different pathogens such as bacteria, filamentous fungi, and viruses are present in raindrops, and these can cause disease in plants.
The researchers hypothesised that plants could recognise rain as a risk factor for disease, and react to protect themselves from the risk in some way.
How Was The Study Conducted?
The researchers conducted a study using Arabidopsis thaliana seedlings to find out how plants respond to rain. This is a small flowering plant native to Eurasia and Africa, and is commonly known as the thale cress. It is significant for plant science research because it is easy and inexpensive to grow, and produces many seeds, thereby allowing extensive genetic experiments.
In order to examine which genes are expressed in the leaves when they are exposed to rain, the researchers started conducting RNA sequencing analyses.
Which Genes Are Expressed In Plants In Response To Rain?
The scientists observed that several major immune-related genes are expressed in response to rain, and that these genes are regulated by immunosuppressive genes called CAMTAs, or calmodulin-binding transcription activators.
Calmodulin regulates gene transcription through transcription factors (TF) including CAMTAs. A transcription factor is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA (mRNA), by binding to a specific DNA sequence. Transcription is the process by which the information in a strand of DNA is copied into a new molecule of mRNA.
According to the study, CAMTAs are controlled by calcium ions (Ca2+), because of which the researchers hypothesised that rain serves to increase Ca2+ levels in cells.
They investigated how Ca2+ levels in Arabidopsis thaliana leaves change in response to rain by introducing GCaMP3 into the leaves. This is a gene that fluoresces green when bound to Ca2+.
The scientists found that when the leaves were exposed to rain, Ca2+ levels around trichomes on leaf surfaces increased, the study said.
Do Trichomes Sense Rain As A Risk Factor And Activate Immune Responses?
The findings suggest that trichomes sense rain as a risk factor and induce calcium waves across the leaf to inactivate the immune suppressor CAMTA. This, in turn, activates immune-related genes. Calcium waves refer to the transmission of localised increases in Ca2+ to the surrounding areas.
In order to confirm the fact that trichomes sense rain as a risk factor and inactivate the immuno suppressor CAMTA to activate immune-related genes, the researchers conducted experiments in the same way using mutants of Arabidopsis which lacked trichomes. They observed that the propagation of calcium waves was compromised in the mutants. This proved that trichomes indeed played a role in inactivating the immuno suppressor CAMTA and activating the immune-related genes.
In a statement issued by Nagoya University, Professor Yasuomi Tada, one of the study authors, said that from these results, the researchers confirmed that trichomes play a role in sensing rain as a risk factor and activating immune responses.
He further said their findings suggest that they may be able to artificially improve plants' defensive capabilities against diseases at any time and for any length of time.
It would be possible to activate crops' immune responses using this technology, when environmental conditions are harsh enough to possibly cause diseases in plants.
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