Improving Phosphorus Efficiency in Crops with Focus on Purple Acid Phosphatase: Potentials and Perspective

Low-phosphorus (P) stress as a key factor limiting plant growth and production is common in most agricultural soils. Most of the soil-applied phosphate will be rapidly immobilized and most of annually applied phosphate fertilizers are fixed in the soil in organic forms by adsorption, sedimentation and transformation. However, excess P application may lead to contamination of water sources by enriching of water bodies with nutrients that cause eutrophication. Thus understanding the mechanisms that are used by plants to cope with low-P stress will be supportive to develop more competent breeding and genetic engineering schemes for generating improved phosphorus efficient crops. To cope with P deficiency and maintenance of phosphate homeostasis, plants have developed different adaptive mechanisms, including alterations in root morphology, recycling of inorganic phosphate (Pi) and induction of acid phosphatases (APases). To establish these strategies, numerous genes are involved in alternative metabolism pathways that are regulated by complex Pi signaling networks. In this review, we intend to summarize current advances in research on the mechanisms of P efficient crops and its breeding strategies, with a particular emphasis on APase and root architecture roles in response to low-P stress.