New Research Shows Plants Have a ‘Nervous System’
New research shows that plants have a “nervous system”, which is constructed differently from an animal one.
Below we present fragments from the respective study.
Rapid, long-distance signaling in plants
A plant injured on one leaf by a nibbling insect can alert its other leaves to begin anticipatory defense responses. Working in the model plant Arabidopsis, Toyota et al. show that this systemic signal begins with the release of glutamate, which is perceived by glutamate receptor-like ion channels (see the Perspective by Muday and Brown-Harding). The ion channels then set off a cascade of changes in calcium ion concentration that propagate through the phloem vasculature and through intercellular channels called plasmodesmata. This glutamate-based long-distance signaling is rapid. Within minutes, an undamaged leaf can respond to the fate of a distant leaf.
Abstract
Animals require rapid, long-range molecular signaling networks to integrate sensing and response throughout their bodies. The amino acid glutamate acts as an excitatory neurotransmitter in the vertebrate central nervous system, facilitating long-range information exchange via activation of glutamate receptor channels. Similarly, plants sense local signals, such as herbivore attack, and transmit this information throughout the plant body to rapidly activate defense responses in undamaged parts. Here we show that glutamate is a wound signal in plants. Ion channels of the glutamate receptor-like family act as sensors that convert this signal into an increase in intracellular calcium ion concentration that propagates to distant organs, where defense responses are then induced, as showed by Masatsugu Toyota, Dirk Spencer, Satoe Sawai-Toyota, Wang Jiaqi, Tong Zhang, Abraham J. Koo, Gregg A. Howe in Glutamate triggers long-distance, calcium-based plant defense signaling published in Science.
Summary
The ability to initiate a rapid defense against biotic attacks and mechanical damage is critical for all organisms. Multicellular organisms have developed mechanisms to systemically communicate the occurrence of a wound to help them escape or defend themselves from predators. Because plants are stationary and cannot escape herbivory, they must respond with chemical defenses to deter herbivores and repair damaged tissue. On page 1112 of this issue, Toyota et al. report long-distance calcium ion signaling in the model plant Arabidopsis thaliana in response to caterpillar herbivory or mechanical wounding. They uncover long-distance calcium signals that require glutamate-like receptor (GLR) channels for signal propagation. These channels are activated by extracellular glutamate, a well-known mammalian neurotransmitter and a more recently uncovered developmental signal in plants. In mammals, glutamate receptors are central to fast excitatory neurotransmission, which is an intriguing parallel to their role as long-distance signals in wounding and defense in plants, as showed by Gloria K. Muday, Heather Brown-Harding, in Nervous system-like signaling in plant defense published in Science
How long ago did plants and animals diverge?
According to a piece in Science Daily (2006), “In 1998 scientists discovered that fungi split from animals about 1.538 billion years ago, whereas plants split from animals about 1.547 billion years ago.” If animals and plants developed these very detailed information-gathering systems independently (convergent evolution), it seems like the unrolling of a project rather than natural selection acting on random mutation (Darwinism). Darwinism doesn’t think ahead like that.
yogaesoteric
June 21, 2019
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