Fine-tuning regulation of strigolactone biosynthesis under phosphate starvation

Abstract

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 upregulated genes in the biosynthesis of strigolactones and their relationship with carotenoids and the hormone abscisic acid (ABA) are discussed.

Keywords: ABA; carotenoids; microarray; phosphate starvation; strigolactones; tomato.

Figure 1

Microarray analysis of the temporally regulated Pi-responsive genes in tomato roots. Numbers of genes induced ≥2-fold under phosphate limiting conditions. Comparison of short-term (6 h), medium-term (24 h) and long-term (96 h) Pi starvation.

Figure 2

Schematic representation of the biosynthesis of strigolactones in plants. The known biosynthetic pathway for carotenoid-derived signalling molecules is shown in white arrows, the proposed pathways for the production of strigolactones in grey arrows. Dotted arrows indicate possible interaction between different components in the scheme. Enzymes: NCED, 9-cis epoxycarotenoid dioxygenase; CCD, carotenoid cleavage dioxygenase. Hormones: ABA, abscisic acid; SMS, shoot multiplication signal. NO indicates no effect.