A genome-wide transcriptional analysis using Arabidopsis thaliana Affymetrix gene chips determined plant responses to phosphate deprivation

Abstract

Phosphorus, one of the essential elements for plants, is often a limiting nutrient because of its low availability and mobility in soils. Significant changes in plant morphology and biochemical processes are associated with phosphate (Pi) deficiency. However, the molecular bases of these responses to Pi deficiency are not thoroughly elucidated. Therefore, a comprehensive survey of global gene expression in response to Pi deprivation was done by using Arabidopsis thaliana whole genome Affymetrix gene chip (ATH1) to quantify the spatio-temporal variations in transcript abundance of 22,810 genes. The analysis revealed a coordinated induction and suppression of 612 and 254 Pi-responsive genes, respectively. The functional classification of some of these genes indicated their involvement in various metabolic pathways, ion transport, signal transduction, transcriptional regulation, and other processes related to growth and development. This study is a detailed analysis of Pi starvation-induced changes in gene expression of the entire genome of Arabidopsis correlated with biochemical processes. The results not only enhance our knowledge about molecular processes associated with Pi deficiency, but also facilitate the identification of key molecular determinants for improving Pi use by crop species.

Glycerolipid transfer for the building of membranes in plant cells

“…Although PC is present in the outer membrane of the plastid envelope, the only known site of PC de novo biosynthesis is localised in the ER. A direct import of PC from ER, or an import of intermediates derived from endoplasmic reticulum PC, possibly DAG or phosphatidate, is therefore required for the synthesis of eukaryotic galactolipids However, the existence of a phospholipase D (PLDζ2) activated by phosphate deprivation [42,43], the accumulation of phosphatidate in the tgd1 mutant and the localization of TGD1 in the chloroplast inner envelope membrane [37] suggest that the transported molecule could be phosphatidate. To understand this latter scheme, the precise localization of the phosphatidic acid phosphatase (PAP) involved in the transformation of eukaryotic phosphatidate into DAG is crucial since part of the eukaryotic DAG is galactosylated by MGD1, the constitutive MGDG synthase that is present in the inner envelope membrane.…”

A phospholipid uptake system in the model plant Arabidopsis thaliana

“…Genome-wide transcriptional analyses showed that ALA10 transcription is upregulated under phosphate starvation 26 . We confirmed these data by quantitative real-time PCR, which demonstrated a highly reproducible 20% increase of ALA10 transcript levels under these conditions (Fig.…”

Role of phosphatidic acid in plant galactolipid synthesis

“…The CDP-DAG pathway is more active in the growth phase but nutrient depletion induces a shift towards the Kennedy pathway [16]. The Kennedy pathway indeed contributes to recycling the polar head of phospholipids such as choline and ethanolamine [20] According to [21] Leaf Root Whole seedling ATS1 Glycerol-3-phosphate acyltransferase through phospholipases D (PLDs) and eventually to remodelling of membranes. The PA phosphatase Pah1p is critical for the shift from the CDP-DAG to the Kennedy pathway because it catalyzes the hydrolysis of PA into DAG, and furthermore because the Pah1p-produced DAG negatively regulates the level of expression of genes encoding the CDP-DAG pathway [16].…”

“…However, it is likely important to distinguish two phases in the lipid response to Pi deprivation. In an early stage, a transient increase of PC precedes the increase of galactolipid synthesis [19] and several phospholipases D and C such as PLDz1, PLDz2, NPC4 and NPC5 are highly overexpressed [20,21]. Therefore, this suggests that, at this stage, the Kennedy pathway actively contributes to remodelling of phospholipids, notably of PE into PC [19].…”

“…With regards to the role of PLDz2 under the initial stage of Pi deprivation and because PLDz2 is located on the membrane of vacuole where Pi is stored (Fig. 1) [20,63], it has been proposed that PA produced by PLDz2 can tune MGDG synthesis as a function of Pi availability. However, because of different roles of PA in multiple cellular functions, activation of MGD1 by PA suggests many different possibilities of control of chloroplast biogenesis through MGDG synthesis.…”