Phosphate starvation responses are mediated by sugar signaling in Arabidopsis

Abstract

Phosphate (Pi) is one of the least available plant nutrients in soils. It is associated with dynamic changes in carbon fluxes and several crucial processes that regulate plant growth and development. Pi levels regulate the expression of large number of genes including those involved in photosynthesis and carbon metabolism. Herein we show that sugar is required for Pi starvation responses including changes in root architecture and expression of phosphate starvation induced (PSI) genes in Arabidopsis. Active photosynthesis or the supplementation of sugar in the medium was essential for the expression of PSI genes under Pi limiting conditions. Expression of these genes was not only induced by sucrose but also detected, albeit at reduced levels, with other metabolizable sugars. Non-metabolizable sugar analogs did not induce the expression of PSI genes. Although sugar input appears to be down-stream of initial Pi sensing, it is absolutely required for the completion of the PSI signaling pathway. Altered expression of PSI genes in the hexokinase signaling mutant gin2 indicates that hexokinase-dependent signaling is involved in this process. The study provides evidence for requirement of sugars in PSI signaling and evokes a role for hexokinase in some components of Pi response mechanism.

A Shoot-Specific Hypoxic Response of Arabidopsis Sheds Light on the Role of the Phosphate-Responsive Transcription Factor PHOSPHATE STARVATION RESPONSE1

“…1B). A light dependency of the low-phosphate response has been previously observed for lupine (Lupinus albus; Liu et al, 2005) and Arabidopsis (Karthikeyan et al, 2007). Interestingly, in these and other studies (Müller et al, 2005), the effect of light was related to the carbohydrates provided via photosynthesis, because sugar addition mimicked or partially restored the low-phosphate response, even in darkness.…”

Expression of Sucrose Transporter cDNAs Specifically in Companion Cells Enhances Phloem Loading and Long-Distance Transport of Sucrose but Leads to an Inhibition of Growth and the Perception of a Phosphate Limitation

“…There is growing evidence that long-distance Suc transport plays an important role in phosphorous responses (Liu et al, 2005;Karthikeyan et al, 2007;White, 2008, 2011). The pho3 mutation, which was identified in a screen for reduced acid phosphatase activity during P limitations, turned out to be a mutant allele of AtSUC2 (Lloyd and Zakhleniuk, 2004).…”

“…The pho3 mutation, which was identified in a screen for reduced acid phosphatase activity during P limitations, turned out to be a mutant allele of AtSUC2 (Lloyd and Zakhleniuk, 2004). Both a reduction in photosynthesis and stem girdling, which blocks phloem transport, attenuate P deficiency responses in roots, including a decrease in the expression of many PSI genes (Liu et al, 2005;Karthikeyan et al, 2007). In addition, it was recently shown that ubiquitous SUT OE can induce a P deficiency response (Lei et al, 2011), potentially by disrupting normal Suc distribution patterns.…”

“…To test if companion cell-specific OE of SUT genes enhances PSI gene expression in the absence of exogenous Suc, representative PSI genes were analyzed by RT-qPCR. AtPT2 (PHT1;4, At2G38940) and PHT2;1 (At3G26570) are inorganic P transporters induced by P starvation (Karthikeyan et al, 2007;Lei et al, 2011). Both had higher expression levels in the SUT OE lines than in the wild type (Fig.…”

The Dual-Targeted Purple Acid Phosphatase Isozyme AtPAP26 Is Essential for Efficient Acclimation of Arabidopsis to Nutritional Phosphate Deprivation

“…PSI gene expression is influenced by sugar levels (Karthikeyan et al, 2006), while exogenous Suc may exacerbate Pi starvation through increased cell proliferation signaling (Lai et al, 2007). As plant cultivation under sterile conditions in the presence of exogenous Suc may generate phenotypes not seen under more physiologically relevant conditions we examined whether soil-grown atpap26 plants displayed any phenotype.…”