Uncoupling phosphate deficiency from its major effects on growth and transcriptome via PHO1 expression in Arabidopsis

Abstract

SUMMARYInorganic phosphate (Pi) is one of the most limiting nutrients for plant growth in both natural and agricultural contexts. Pi-deficiency leads to a strong decrease in shoot growth, and triggers extensive changes at the developmental, biochemical and gene expression levels that are presumably aimed at improving the acquisition of this nutrient and sustaining growth. The Arabidopsis thaliana PHO1 gene has previously been shown to participate in the transport of Pi from roots to shoots, and the null pho1 mutant has all the hallmarks associated with shoot Pi deficiency. We show here that A. thaliana plants with a reduced expression of PHO1 in roots have shoot growth similar to Pi-sufficient plants, despite leaves being strongly Pi deficient. Furthermore, the gene expression profile normally triggered by Pi deficiency is suppressed in plants with low PHO1 expression. At comparable levels of shoot Pi supply, the wild type reduces shoot growth but maintains adequate shoot vacuolar Pi content, whereas the PHO1 underexpressor maintains maximal growth with strongly depleted Pi reserves. Expression of the Oryza sativa (rice) PHO1 ortholog in the pho1 null mutant also leads to plants that maintain normal growth and suppression of the Pi-deficiency response, despite the low shoot Pi. These data show that it is possible to unlink low shoot Pi content with the responses normally associated with Pi deficiency through the modulation of PHO1 expression or activity. These data also show that reduced shoot growth is not a direct consequence of Pi deficiency, but is more likely to be a result of extensive gene expression reprogramming triggered by Pi deficiency.

Maize Source Leaf Adaptation to Nitrogen Deficiency Affects Not Only Nitrogen and Carbon Metabolism But Also Control of Phosphate Homeostasis

“…One of the down-regulated SPX domain proteins in the N-deficient maize leaves belonged to the PHO1 like subfamily, and the proteins are supposed to be involved in Pi loading into the xylem, Pi sensing, and sorting of proteins to the endomembranes (Wang et al, 2004). Interestingly, by down-regulation of the PHO1 gene in Arabidopsis, it was recently possible to partly uncouple the Pi deficiency signal from the growth response, and plant shoots showed normal biomass accumulation despite a significant decrease in Pi supply (Rouached et al, 2011). Transgenic manipulation of Pi regulators had also impact onto the cold adaptation of plants (Hurry et al, 2000;Zhao et al, 2009).…”

Phosphate homeostasis in the yeast Saccharomyces cerevisiae, the key role of the SPX domain‐containing proteins

“…In plants, although none of these proteins have yet been characterized as Pi transporters, several proteins possessing the SPX domain have been shown to be major regulators of Pi homeostasis, being involved in Pi signaling, remobilization, export [10,[14][15][16][17][18][19][20]. Moreover, recent work in both yeast and plants report that the SPX domain itself could be involved in fine-tuning of Pi transport and signaling, through mechanisms such as physical interactions with other proteins [12,13,21].…”

Phosphorus Transport in Arabidopsis and Wheat: Emerging Strategies to Improve P Pool in Seeds

“…These observations indicate the existence of additional unknown genes and pathways regulating the Pi content in plants [8,52]. For instance, it is now well established that Pi content in plants is altered when plants are challenged by zinc limitation (−Zn) [6,[76][77][78][79].…”

“…Intriguingly, under single −Zn stress, an excess of Pi supply causes loss of wheat biomass in comparison with plants grown under -P-Zn simultaneous stress [78]. Nevertheless, despite its fundamental importance, very little is known about the regulatory network established during Zn deficiency to control Pi homeostasis [52]. Studying Zn/Pi homeostasis interactions will lead us to uncover new genes and pathways controlling plant Pi homeostasis.…”