Phosphorus starvation response in plants and opportunities for crop improvement

Abstract

Phosphorus (P) is one of the most essential nutrients for the adequate growth and development of plants as well as a crucial component of all life forms. Plants absorb P only in the inorganic form of orthophosphate (Pi). The availability of soluble Pi in most of the world's soil is poor as compared to its requirement for optimum growth and crop yield. Application of P fertilizers is a common practice to grow crop plants in P-poor soils. However, highly reactive Pi easily forms insoluble complexes in soil and a large fraction of applied Pi fertilizer becomes unavailable to plants. This problem is further compounded as the source of P fertilizers (i.e., P rocks) may be exhausted in the near future. Plants have evolved physiologically, biochemically, and morphologically to cope with Pi starvation through modification of the root system architecture for better Pi uptake and remobilize the internal Pi content. Genetic regulation of these adaptations has been explored to some extent and thus provides the resource for crop improvement using transgenics or plant breeding approaches. This complex network is regulated by transcription factors, microRNAs, membrane transporters, kinases/phosphatases, ubiquitin conjugase, and various hormones. Sugars have also been shown to play important roles in Pi starvation-mediated gene expression. Here, we review the recent progress made in delineating the functions of genetic elements in terms of modulating the Pi starvation response in plants. We further explore the possible strategies for crop improvement using available resources.