Plant researchers from Kiel analyse the influence of genetic information on the onset of plant flowering using the example of thale cress
All flowering plants pass through a flowering period at the transition from the growth to the reproductive phase. Its beginning is determined by complex plant regulatory mechanisms. It also depends on environmental conditions, including temperature and day length. The determination of the start of flowering is an important lever with which plants can react to variable environmental conditions. A flowering plant adapts to drought or higher temperatures by, for example, bringing forward flowering under unfavourable conditions. In this way, it tries to start its reproductive phase earlier and still ensure that it can reproduce. A better understanding of the relationship between plant control and environmental influences is therefore important for assessing the susceptibility or resistance of different plants to climate change and the associated changes in agricultural cultivation conditions. Plant researchers around the world are therefore investigating the mechanisms involved in the control of flowering, including their genetic regulation.
Last year, a research team from the Botanical Institute at Kiel University demonstrated the involvement of the so-called POCO1 protein in the regulation of flowering time in a frequently studied plant model organism, the thale cress (Arabidopsis thaliana). In a follow-up paper recently published in the journal BMC Plant Biology, researchers from the Department of Botanical Genetics and Molecular Biology headed by Professor Frank Kempken analysed the genetic basis of these proteins, plant ribonucleic acid (RNA), using high-throughput sequencing methods. This enabled them to identify the genetic expression and variation of these proteins, which in Arabidopsis are associated with the regulation of flowering time.
Differences in the genetic repertoire
In order to investigate the so-called gene expression associated with flowering, the research team active at the Kiel Plant Center (KPC) at Kiel University carried out comparative analyses of plants at different stages of development - in each case in early flowering so-called poco1 plants and the unaltered wild types. The research team compared identical developmental stages in both variants and was able to identify significant differences: "The differences are particularly evident, for example, in a particular group of genes," emphasizes Hossein Emami, a research associate in Kempken's Kiel research group. "These include the so-called 'Flowering Locus T' (FT) gene, which is regulated very differently in poco1 and wild type plants," Emami continues. The upregulation of the FT gene is therefore probably directly related to an earlier flowering time of the thale cress.
In addition, the Kiel researchers investigated a second mechanism involved, which they had also discovered in the previous work. A number of genes in Arabidopsis seem to be related to a specific plant signalling pathway, which is usually downregulated in early flowering plants. These so-called ABA signals are responsible for the production of a flower-inhibiting plant hormone that needs to be deactivated at the transition from the growth to the reproduction phase. Gene expression analysis showed that the genes responsible for ABA signals were downregulated in early flowering plants compared to the wild type. "These signals therefore play another key role in controlling flowering time. Their inhibitory effect on the onset of plant reproduction can therefore be switched off under stress conditions, as the downregulated expression of the genes involved suggests," Emami continues.
Gene regulation contributes to early flowering
The Kiel research team was thus able to confirm the mechanisms of flowering time control by means of their global gene expression analysis. The up- and downregulation of certain genes therefore apparently also contributes to the fact that the POCO1 protein can additionally intervene in the ABA signalling pathway and thus trigger up to four days earlier flowering. As a consequence, further stress-related genes, in particular those associated with drought, appear in the early flowering plants, which can be seen, among other things, in the drought sensitivity of these plants.
"In summary, we have discovered that a certain genetic variant in Arabidopsis, which is responsible for an earlier flowering time, also leads to a number of other regulatory adaptations," said Kempken. "This includes, for example, the cellular mechanisms of flowering time control or the regulation of stomata to control water losses. Overall, this will help us to better understand the genetic characteristics that are expressed in early-flowering plants and that cause them to deviate from the wild type," Kempken continues. The KPC research team thus identified another important building block that will improve our understanding of plant flowering time regulation, especially under stress conditions, in the future. These findings could help plant breeding in the future to adjust the flowering time of important crops so that they can continue to grow even under drastically changed climatic conditions.
Hossein Emami, Abhishek Kumar and Frank Kempken (2020): Transcriptomic analysis of poco1, a mitochondrial pentatricopeptide repeat protein mutant in Arabidopsis thaliana. BMC Plant Biology First published 12 May 2020