To increase crop production with fewer fertilizers: The relevance of the phosphate

Phosphate (Pi) is an essential nutrient for all organisms. Pi is non-uniformly distributed in soils and its scarcity causes severe losses in crops productivity. To alleviate this and to increase crop yield, large amounts of fertilizers are normally applied. However, the majority of Pi is not absorbed by the plants and ends into the fresh water, generating severe environmental problems as well as economic losses for the farmers.

Roots are underground organs involved in nutrients uptake and, therefore, now are the focus of genetic improvement to generate more nutrient-efficient plants. However, the majority of the root biology studies in vitro have been done growing the root system in the presence of light. In this work, we showed that root illumination compromises the Pi starvation response (PSR) at different levels. Thus, we have analyzed morphological, transcriptional and physiological responses to Pi starvation in dark-grown roots, using the D-Root system that was previously developed in our lab. In these new conditions, we have identified novel genes and pathways regulated by Pi starvation that were not described previously, which could be targets for genetic improvement. We also showed that Pi-starved plants increase the cis-zeatin (cZ) hormone, an isomer that was thought to have low biological activity. However, using transcriptomic analyses we found that cZ regulates a specific set of genes that improve the plant response to phosphate shortage, increasing the size of the root system as well as root hairs length. This responses increase the total absorbing surface and potentiate the search for new phosphate-rich areas.