Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2003
Publication Date: N/A
Citation: Interpretive Summary: Phosphorus (P) is a major nutrient for crops, and lack of P frequently limits plant growth. Addition of P fertilizer to crops is costly, and it is predicted that inexpensive sources of P will expire in 40 to 60 years. Thus, it is extremely important that we learn how plants adapt to insufficient P in soils. The legume plant white lupin has a very unique adaptation to acquire P from soils that are low in P. It forms masses of fine roots called proteoid roots. Proteoid roots secrete many compounds into the soil-root boundary that help to solubilize soil P into forms the plant can use. The adaptive processes require the expression of many genes. In efforts to understand which genes are turned on as white lupin adapts to P stress, we isolated and sequenced some 2,000 genes derived from gene libraries made at two different stages (an early stage and a later stage) of proteoid root formation. Our data show that under low P stress conditions, at least 35 novel genes are turned on. These genes include those involved in: P uptake and recycling; organic acid exudation by roots; altered metabolism; synthesis of plant hormones; and recognition of environmental stress. This discovery is important because it provides us with information and tools to use in efforts to develop crops that are more efficient in obtaining P from soil. Plants that are more efficient in obtaining P will reduce the need for expensive fertilizer and lead to more sustainable farming practices.
Technical Abstract: White lupin (Lupinus albus L.) adapts to phosphorus deficiency (-P) by the development of short, densely clustered lateral roots called proteoid (or cluster) roots. In an effort to better understand the molecular events mediating these adaptive responses, we have isolated and sequenced 2,102 expressed sequence tags (ESTs) from cDNA libraries prepared with RNA isolated at different stages of proteoid root development. Determination of overlapping regions revealed 322 contigs (redundant copy transcripts) and 1,126 singletons (single copy transcripts) that compile to a total of 1,448 unique genes (unigenes). Nylon filter arrays with these 2,201 ESTs from proteoid roots were performed to evaluate global aspects of gene expression in response to -P stress. ESTs differentially expressed in P-deficient proteoid roots compared to +P and -P normal roots include genes involved in carbon metabolism, secondary metabolism, phosphorus scavenging and remobilization, plant hormone metabolism, and signal transduction.