Submitted to: Proceedings of International Conference on Root Biology
Publication Type: Proceedings
Publication Acceptance Date: 3/5/1998
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Phosphorus, an essential nutrient for plants, is becoming limited in many arable soils. White lupin has evolved several mechanisms for scavenging phosphate. We have characterized a suite of responses in lupin roots that occur during P-deficient conditions. Proteoid root segments are clearly visible by 9 days after emergence (DAE), and within 24 hours, higher PEPC mRNA levels are observed in the proteoid segments. In the following 48 hours, higher PEPC and APase activities are observed, and enhanced organic acid exudation is detected. It appears that the responses, including the initiation of enhanced proteoid root formation and citrate acid exudation in lupin, are coordinated. Further work studying the regulation of PEPC and APase expression, and the role of plant growth regulators in proteoid root formation will provide insight into the adaptive mechanisms used by white lupin to overcome P-deficiency. Phosphate regulated gene expression has been well characterized in bacteria and fungi. In Escherichia coli, a regulatory element, pho B, is induced during P-deficient conditions which regulates up to 20 genes. The Pi status in E. coli has been found to regulate up to 3% of the entire genome. Characterization of coordinated responses to P-stress in many plants suggests that higher plants may also contain P-driven regulatory mechanisms, although a comparable pho regulon has not been found, to date, in higher plants. Further studies of the biochemical and molecular responses of higher plants are needed to define features controlling plant responses to nutritional deficiencies, and confirm the existence of a pho-like regulon. The coordinated anatomical and biochemical changes that occur in white lupin roots make it a useful model for studying the responses of higher plants to P-deficiency.