Scientists Shed Light On How Plant Recognizes And Accommodates Its Useful Microbial Partners

Arabidopsis CNGC19 calcium channel is very important for maintenance of balance between plant immunity and controlled colonization of plant roots, which results in growth promotion of host plant.

APR 30, 2020 | BY RATNESHWAR THAKUR

Ever wondered how does a plant welcome a friendly fungi? How do the plant roots turn on and off its defence mechanisms to an array of good and bad fungi in its vicinity? These intriguing questions have been addressed by Dr. Jyothilakshmi Vadassery’ research team at DBT- National Institute of Plant genome Research, New Delhi using model plant Arabidopsis thaliana and the growth promoting fungi, Piriformospora indica isolated from Indian Thar desert.

The study has been published in the 'Journal of Experimental Botany'.

Plants roots come in contact with several soil microbes as they grow. Some microbes are bad for plants and some good for their health. Piriformospora indica is a good fungus that colonizes the roots of many plant species and promotes their growth, increases nutrient uptake. P. indica also imparts abiotic and biotic stress tolerance to a wide array of host plants.

Plant uses many different chemicals and permeable ionic channels to send and receive signals. Among these, calcium signaling operates through calcium permeable channels present in the plasma membrane and many organelles like endoplasmic reticulum, chloroplast and nuclear membranes of plant cells. Through these calcium channels, plant uses calcium ions to communicate and drive cellular processes.

Activation of calcium signaling in plant roots is a crucial event for perceiving P. indica. Increase in cellular calcium levels in plant roots is associated with increased plant defense. Calcium elevations are produced in cells upon opening of ion channels that are activated when cells perceive stimuli.

“To know how plant root interacts with fungus P. indica and recognize it as good interacting partner, we studied all the genes induced upon fungal stimuli. We found that cyclic nucleotide gated calcium channel 19 (CNGC 19) is highly induced upon fungal colonization,” said Dr. Abhimanyu Jogawat, SERB postdoctoral fellow at NIPGR, New Delhi and the first author of the study.

NIPGR team generated a transgenic plant that does not have CNGC19 gene. In these lines (cngc mutant lines) they saw increased colonization of P. indica and a growth inhibition (and not growth promotion as expected) due to uncontrolled colonization.

Previous study suggests that when roots of Arabidopsis plants were treated with cell wall extracts of fungus (P. indica), it induces elevation of cytosolic Ca²⁺ (Ca²⁺_cyt ) which is important for the beginning of symbiotic interactions and promoting growth. In the present study, P. indica cell wall extract induced Ca²⁺ elevation is reduced in cngc19 mutant indicating a role in the generation of Ca²⁺_cyt elevation.

“Our study has shown that Arabidopsis CNGC19 calcium channel is very important for maintenance of balance between plant immunity and controlled colonization of plant roots, which results in growth promotion of host plant. Our study will help plant scientists to understand how plant recognizes and accommodates its useful microbial partners without causing harmful effects and by not compromising on its ability to detect harmful microbes,” said the study leader Dr. Jyothilakshmi Vadassery.

The research team involved Jogawat A, Meena MK, Kundu A, Varma M, Vadassery J. The study was funded by the Department of Biotechnology (DBT), India through a NIPGR core grant, SERB- NPDF, MPG-India partner group program of the Max Planck Society (Germany) and Department of Science and Technology (DST), India.

Journal Reference:
Calcium channel CNGC19 mediates basal defense signaling to balance colonization of Piriformospora indica on Arabidopsis roots

Ratneshwar Thakur
Biologist | Science Communicator | Science Writer

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