Strigolactones are signalling molecules playing a double role in the rhizosphere as host detection signals for arbuscular mycorrhizal (AM) fungi and root parasitic plants. They are biosynthetically originating from carotenoids. The biosynthesis of these signalling compounds is tightly regulated by environmental conditions such as nutrient availability, mainly phosphate (Pi). However, although it is known that limited-Pi conditions improve the production and/or exudation of strigolactones, there is no information concerning the effect of these conditions on the enzymes involved in strigolactone production. We have recently demonstrated that tomato is a good system to study the production and regulation of these important signalling compounds.1 In the present paper we describe an analysis of Pi starvation-induced changes in gene expression in tomato roots using a microarray study. The possible role of the up-regulated genes in the biosynthesis of strigolactones and their relationship with carotenoids and the hormone abscisic acid (ABA) are discussed.