Arabidopsis PHL2 act as the key component of the central regulatory system controlling transcriptional responses to phosphate starvation

We first compared the transcriptomes of the roots of WT seedlings grown under P+ and P- conditions. Using a 2-fold change and a FDR (false discovery rate) of <0.05 as the cut-off for selecting the differentially expressed transcripts, we found that the expression of 581 genes was induced and that the expression of 120 genes was repressed by Pi starvation. We then compared the expression levels of these 581 PSI genes in the WT and phl2. The results showed that the average expression level of these genes was 51% lower in phl2 relative to the WT. If we arbitrarily defined a 30% reduction in the expression level of PSI genes as “a significant reduction”, the expression of 87.6% of PSI genes was significantly reduced in P- phl2 relative to P- WT seedlings. Thus, we conclude that PHL2 is a key component of the central regulatory system controlling transcriptional responses to Pi starvation. Overall design: We performed a RNA-seq analysis on WT and phl2 plants. Total RNAs were extracted from the roots of P+ and P- WT seedlings (i.e., seedling grown on P-sufficient and P-deficient media) and of P- phl2 seedlings. The extracted RNAs were subjected to RNA deep sequencing. Our RNA-seq analyses showed that among the 581 PSI genes, the expression of 87% is significantly reduced in phl2, demonstrating that PHL2 positively regulates the transcription of a large number of PSI genes at the genomic level