Sexual plant reproduction: Male and female talk in the same way as do cells in your brain

Working in the IGC laboratories, the team used an extensive combination of genetic, pharmacologic 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: the molecular nature of calcium channels in the outer membrane of plant cells, a central question in plant physiology elusive for more than 20 years, and what are 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.

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, the researchers showed 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. Furthermore, D-serine activates the GLRs on the tips of pollen tubes, allowing calcium ions to flow into the tube. They took their research a step further demonstrating that D-serine is indeed produced in the female sexual organs, and that 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.

During the growth of the pollen tube (in this case of Arabidopsis), the concentration of calcium within varies from higher concentration (red signal) to lower concentrations (blue signal).

(Photo Credit: Jose Feijo / Instituto Gulbenkian de Ciencia)

José Feijó says "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. Our findings, implicating analogous genes in growth processes in both plants and animals, underscores how evolution re-uses successful mechanisms, over and over again. We feel that our research, performed in Arabidopsis and tobacco, now opens doors for the study of conserved cell-cell communication processes, across plant and animals species".

This is a microscope image of the pollen grains germinating at the stigma of the weed Arabidopsis Thaliana.

(Photo Credit: Jose Feijo / Instituto Gulbenkian de Ciencia)

1- José Feijó; 2- Erwan Michard, first author of the research article; 3- Pedro Lima, 4- Filipe Borges, 5- Ana Catarina Silva: also authors of the research article members of team at IGC.

(Photo Credit: Jose Feijo / Instituto Gulbenkian de Ciencia)

Source: Instituto Gulbenkian de Ciencia