Phosphorus (P) is an essential macronutrient for plant growth and development. Upon P shortage, plant responds with massive reprogramming of transcription, the
Phosphate Starvation Response (PSR). In parallel, the production of strigolactones (SLs)-a class of
plant hormones that regulates plant development and rhizosphere signaling molecules-increases. It is unclear, however, what the functional link is between these two processes. In this study, using tomato as a model, RNAseq was used to evaluate the time-resolved changes in gene expression in the roots upon P
starvation and, using a tomato
CAROTENOID CLEAVAGE
DIOXYGENASES 8 (CCD8) RNAi line, what the role of SLs is in this.
RESULTS: Gene ontology (GO)-term enrichment and KEGG analysis of the genes regulated by P
starvation and P replenishment revealed that metabolism is an important component of the P
starvation response that is aimed at P homeostasis, with large changes occurring in glyco-and
galactolipid and carbohydrate metabolism, biosynthesis of secondary metabolites, including
terpenoids and
polyketides,
glycan biosynthesis and metabolism, and
amino acid metabolism. In the CCD8 RNAi line about 96% of the PSR genes was less affected than in wild-type (WT) tomato. For example,
phospholipid biosynthesis was suppressed by P
starvation, while the degradation of
phospholipids and biosynthesis of substitute
lipids such as
sulfolipids and
galactolipids were induced by P
starvation. Around two thirds of the corresponding transcriptional changes depend on the presence of SLs. Other biosynthesis pathways are also reprogrammed under P
starvation, such as phenylpropanoid and
carotenoid biosynthesis, pantothenate
and CoA,
lysine and
alkaloids, and this also partially depends on SLs. Additionally, some
plant hormone biosynthetic pathways were affected by P
starvation and also here, SLs are required for many of the changes (more than two thirds for
Gibberellins and around one third for
Abscisic acid) in the gene expression.
CONCLUSIONS: