Real-time RT-PCR profiling of transcription factors including 34 MYBs and signaling components in white lupin reveals their P status dependent and organ-specific expression

Phosphorus (P) is often a limiting macronutrient because of its low availability in soils. White lupin (Lupinus albus L.) plants are well adapted to growth under low-P conditions. White lupin acclimation to low-P conditions includes changes in root architecture and enhanced expression of numerous genes encoding for secreted acid phosphatases and phosphate transporters. However, information about transcription factors and signaling proteins that coordinate the P-starvation responses is limited in white lupin. In this study, cDNAs and ESTs encoding for transcription factors and signaling proteins were isolated and their transcription profiles were clarified to facilitate the identification of key signal transduction genes necessary to improve P acquisition, allocation, and use. 34 cDNA fragments of MYB-coiled coil (MYB-CC) and R2R3-MYB, and 26 ESTs encoding for transcription factors and signaling proteins were isolated. Four MYB-CC cDNAs showed high similarity to the transcription factor Phosphate starvation response 1 in Arabidopsis, which has been implicated in regulation of many P-starvation response genes. In addition, deduced amino acid sequences of 29 R2R3-MYB cDNAs showed similarities to Arabidopsis R2R3-MYB proteins. Transcription of the 60 genes, as measured by real-time reverse transcription-PCR, in normal roots, cluster roots, leaves, and shoot tips under P sufficient and low-P conditions revealed that six (10%) and two (3.3%) sequences were either induced or suppressed, respectively, by low-P condition. In addition, 36 genes (60%) showed an organ specific expression.