The availability of soil phosphorus (P), an essential element, is one of the most important requirements for plant growth and crop production. The morphological and physiological adaptations evolved by plants to cope with P starvation have been well characterized. Several P deficiency plant responses are regulated at the transcriptional level. Microarray analysis has generated valuable information on global gene expression in Arabidopsis thaliana grown under P-stress. Despite the identification of P responsive genes, little is known about the regulation of gene expression changes. Four transcription factors, PHR1, WRKY75, ZAT6 and BHLH32, involved in P starvation signaling have been characterized in Arabidopsis, and signaling pathways are deciphered. This review analyzes the current knowledge of transcriptional regulation of P starvation responses in Arabidopsis vis-a-vis legumes such as lupine, common bean and Medicago truncatula. The knowledge on regulatory and signaling mechanisms involved in P acquisition and use in legumes will be useful for improvement of these crops, which account for a large proportion of the worlds crop production, providing good nutritional quality feed and food.