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Male and female plant organs talk like brain cells

Male and female plant organs communicate in the same way as brain cells, according to research by scientists in Portugal. A study published in the journal Science shows how pollen, which contains the plant's male gametes, communicates with the plant's female organ using a mech...

Male and female plant organs communicate in the same way as brain cells, according to research by scientists in Portugal. A study published in the journal Science shows how pollen, which contains the plant's male gametes, communicates with the plant's female organ using a mechanism commonly observed in the nervous system of animals. According to the researchers, the study reveals a new mechanism underlying reproduction in plants and opens an exciting new avenue in the study of how cell-cell communication is conserved between animals and plants. Plant reproduction is a complex and highly coordinated process. Pollen grains, which contain the plants' male gametes (sperm cells), are carried from the male organ of the flower (the stamen) to the female organ (the pistil). Here the pollen germinates and grows a pollen tube, which extends and is guided to the ovary, where it releases the sperm. The sperm fuse with the egg cells, giving rise to an embryo, part of the seed. In this study, researchers from the Instituto Gulbenkian de Ciência (IGC) studied the development of the pollen tubes in the pistil. According to the researchers, while biologists have, for many years, observed regular oscillations in several parameters that control the growth of pollen tubes, the actual molecular channels that control these oscillations and their physiological output have remained elusive. Dr José Feijó, group leader at the IGC and Professor at Lisbon University, and his colleagues have filled this knowledge gap with the discovery that in tobacco and the weed Arabidopsis, oscillations of calcium ions in the growing pollen tubes are facilitated by channels called Glutamate receptors-like (GLRs). Moreover, they found that these channels are opened by, amongst other components, a rare amino acid known as D-serine (D-Ser). Both D-Ser and GLRs are not only found in plants; they are also key molecules in cell-cell communication in the animal central nervous systems. They play a central role in memory and learning processes in the brain, and have been implicated in a wide range of neurodegenerative diseases such as multiple sclerosis, Alzheimer's, Huntington's disease and others. 'And now, surprisingly, they also have a role in reproduction of plants,' noted the researchers. The team used an extensive combination of genetic, pharmacological and electrophysiological techniques to reveal the role of glutamate receptor-like (GLRs) genes and D-serine in pollen grains, and their physiological impact on plant reproduction. In proving that GLRs are calcium channels, the team also solved two long-standing riddles in plant biology, namely the molecular nature of calcium channels in the outer membrane of plant cells. They also revealed the functions of GLRs genes in plants, a fact that has puzzled biologists ever since the first genome of the model plant Arabidopsis was sequenced. The team's investigations revealed that impairing the GLR functions in male gametes leads to partial male sterility: fewer seeds are produced by the plant, and the pollen tubes are abnormal. Regarding D-serine, the team found that it activates the GLRs on the tips of pollen tubes, allowing calcium ions to flow into the tube. They took their research a step further by demonstrating that D-serine is indeed produced in the female sexual organs, and that the absence of D-serine in these organs also leads to deformed pollen tubes. Together, these findings strongly suggest that D-serine produced in the female sexual organs may have a role in guiding pollen tubes to their final target. Dr José Feijó commented that 'pollen tubes are a model system for cellular tip-growth, a process common to fission yeast, filamentous fungi, the root hairs of plants and nerve cells'. He said that his group's work, 'implicating analogous genes in growth processes in both plants and animals, underscores how evolution re-uses successful mechanisms, over and over again'. Dr Feijó said the research 'performed in Arabidopsis and tobacco, now opens doors for the study of conserved cell-cell communication processes, across plant and animals species'.For more information, please visit: Instituto Gulbenkian de Ciência (IGC):http://www.igc.gulbenkian.pt/Science Express:http://www.sciencemag.org/content/early/recent

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