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Primary hypoxia signalling in plants

Final Report Summary - HYPOXSI (Primary hypoxia signalling in plants)

The research part of this Marie Curie ERG project aimed to 1) identify primary hypoxia responsive genes, 2) identify components of the hypoxia signalling pathway and 3) define the relation between these.

A number of genes collected from literature, were analysed for their usefulness as early hypoxia markers (primary hypoxia responsive genes) in the model plant Arabidopsis. Testing the behaviour of these genes in a newly developed hypoxia setup (see Figure 1) showed that ADH1 was the most hypoxia-responsive gene, increasing >500-fold after a 2-hour hypoxia treatment (aim 1; see Figure 2). Subsequently a pADH1::LUC reporter was characterised for its use in a mutant screening. Although, the luminescent signal was sufficiently detectible to perform low-throughput experiments, it was not robust enough to be used for high-throughput screening of thousands of individuals. Even application of state-of-the-art imaging techniques, which allowed integration of the luminescent signal over a longer periods of time (applied in collaboration with Dr. A.R. van der Krol, Wageningen University, The Netherlands), did not render a reliable assay (see Figure 3). As an alternative strategy, expression of ADH1 could be determined reliably by qPCR techniques. This method was applied to a large set of Arabidopsis ecotypes (see Figure 4), potentially enabling gene the identification of signalling components via genome-wide association mapping. The study resulted in the identification of a number of loci putatively involved in the hypoxia signalling pathway (aim 2; see Figure 5). Fine mapping of selected cross populations was not possible within the project period and thus isolation of the underlying genes and elucidation of their relation (aim 3) awaits further studies.
In a parallel study on an ecologically relevant species, Solanum dulcamara, the signalling pathway leading to morphological adaptations to submergence/hypoxia was investigated. Genome-wide expression analyses identified a set of early responsive genes (aim 1) and indicated the involved of the plant hormones ethylene, auxin and abscisic acid in the signalling pathway (aim 2). Subsequent physiological studies confirmed this.

The above studies have already led to several scientific publications and are being continued. Furthermore, they contributed to a good integration of the fellow at the host institute, and the fellow now supervises several PhD students within the institute (see http://www.ru.nl/bsweet/). The fellow has also passed his probationary period and secured a permanent position. Furthermore, the scientific achievements of the fellow in the field of abiotic stress tolerance in plants has enabled him to obtain additional research grants, also in collaboration with plant breeding companies, with the aim of valorisation of results obtained (see http://www.ru.nl/mpp/people/virtuele-map-people/ivo-rieu/).

The work on hypoxia signalling in Arabidopsis is still at a fundamental stage and more progress on deciphering the pathway is needed before socio-economic impact can be expected. The parallel research on submergence/hypoxia responses in Solanum dulcamara has a high short-term potential for social-economic impact, through improvement of crop species. A study aimed at introgressing submergence resistance traits into tomato was co-funded by a plant breeding company.