In the higher plants, branches are formed from small structures known as axillary buds, located at the base of the leaves. Axillary buds contain a compressed version of the branch, and are only activated and elongate in favourable environmental and internal conditions. Otherwise they remain dormant.
A study by scientists at the Centro Nacional de BIotecnología of the CSIC (CNB-CSIC) shows that genes activated by lack of nutrients (known as carbon-starvation genes) are linked to this decision in the bud: grow or wait for more appropriate conditions. The paper was published in the journal Frontiers in Plant Science.
According to the researchers, this response closely resembles that of any other animal, plant or yeast cell that has little available sugar. If there are few nutrients, the cell stops growing.
"In axillary buds, this genetic response takes place even before sugar is scarce," says Pilar Cubas, a CNB-CSIC researcher and lead author of the paper. “It is sufficient that the plant anticipates a situation in which it will undergo a sugar fast (short days, large amounts of infrared light, etc.) and the buds go into saving mode and try not to use more than is strictly necessary.”
This study was carried out on one herbaceous (Arabidopsis thaliana) and two woody species (poplar and grapevine). "The pattern of active genes coincides in the dormant buds of these three very different species. This indicates that these genes are highly conserved in evolution, with a very important role in dormancy in the higher plants," explains Cubas.
Keeping buds in the dormant state allows plants to withstand drought, poor soil, poor light, and other adverse conditions. In woody plants, many buds remain dormant from summer/autumn to the following spring. The scientists believe that this ability has allowed plants to colonize habitats with fluctuating conditions in which continued growth would not be possible.
Both plant development experts and bioinformaticians collaborated in the study. Together they identified the shared genes that induce the dormant state in buds of the different species.
"Now we are trying to understand how the perception of the signals that allow plants to anticipate times of carbon and energy shortage are related to triggering savings mode responses in the axillary bud in these situations," explains Cubas.
- Tarancón Carlos, González-Grandío Eduardo, Oliveros Juan C., Nicolas Michael, Cubas Pilar. A Conserved Carbon Starvation Response Underlies Bud Dormancy in Woody and Herbaceous Species. Frontiers in Plant Science 2017; 8:788 10.3389/fpls.2017.00788