The root system of a plant constantly provides the stems and leaves with water and dissolved minerals. To accomplish this, the roots must grow into new regions of the soil.
Plant roots can grow anywhere, without any limit. To grow, they need to balance the production of new cells via cell division and elongation. In this balancing act, plant hormones called Brassinosteroid (BR) are indispensable.
BR hormones play a vital role in root growth and control cell division and cell elongation by establishing and increasing signaling gradient along the longitudinal root axis. The signaling cascade initiated by this hormone is particularly active in the root elongation zone, but how brassinosteroid signaling is explicitly triggered in this region remains unknown.
In this study, the team of Dr. Jenny Russinova (VIB-UGent Center for Plant Systems Biology) unravels how brassinosteroid production is localized in plant roots for optimal growth patterns.
Dr. Jenny Russinova (VIB-UGent): “Because brassinosteroid hormones play a role in plant stress tolerance, the tools generated in this work will permit monitoring brassinosteroid hormone distribution in response to different biotic and abiotic stresses. Thus, our observation will have a large impact on our understanding of plant performance under climate change scenarios.”
In this study, scientists used conventional confocal microscopy and a custom-made spinning disk microscope to observe vertical plant growth (in the plant model Arabidopsis thaliana) in the Fendrych lab. They observed how plants, by controlling expression levels of brassinosteroid biosynthetic enzymes, can restrict the domain of hormone production.
They found that the locally restricted synthesis of the hormone controls brassinosteroid signaling in different root zones of the plant.
Scientists then measured hormone levels and confirmed that brassinosteroid levels are kept at low levels in proliferating cells at the tip. It was observed that higher hormone concentrations are produced in the root elongation zone.
Dr. Nemanja Vukasinovic (VIB-UGent Center for Plant Systems Biology) said: “Our research revolved around the fact that brassinosteroids are hydrophobic compounds and, as such, are unlikely to be highly mobile within the plant tissues. We reasoned that it would make sense to study localization patterns of brassinosteroid biosynthetic enzymes to examine how the hormone is distributed. It turned out that this was a good idea since those patterns revealed increased enzyme expression levels in the elongation zone. That was the main discovery around which we built all other experiments.”
The work was performed in collaboration with the Strnad lab in Olomouc (Czech Republic).
- Vukašinović, Wang, et al. (2021). Local brassinosteroid biosynthesis enables optimal root growth. Nature Plants. DOI: 10.1038/s41477-021-00917-x