Organ-specific phosphorus-allocation patterns and transcript profiles linked to phosphorus efficiency in two contrasting wheat genotypes

Recent studies have identified genotypic variation in phosphorus (P) efficiency, but rarely have the underlying mechanisms been described at the molecular level. We demonstrate that the highly P-efficient wheat (Triticum aestivum L.) cultivar Chinese 80-55 maintains higher inorganic phosphate (P-i) concentrations in all organs upon P-i withdrawal in combination with higher P-i acquisition in the presence of P-i when compared with the less-efficient cultivar Machete. These findings correlated with differential organ-specific expression of P-i transporters TaPHT1;2, TaPHT1;5, TaPHT1;8, TaPHT2;1 and H+-ATPase TaHa1. Observed transcript level differences between the cultivars suggest that higher de novo phospholipid biosynthetic activities in P-i-limited elongating basal leaf sections are another crucial adaptation in Chinese 80-55 for sustaining growth upon P-i withdrawal. These activities may be supported through enhanced breakdown of starch in Chinese 80-55 stems as suggested by higher TaGPho1 transcript levels. Chinese 80-55 fine roots on the other hand show strong suppression of transcripts involved in glycolysis, transcriptional regulation and ribosomal activities. Our work reveals major differences in the way the two contrasting cultivars allocate P-i and organic P compounds between source and sink tissues and in the acclimation of their metabolism to changes in P-i availability.