Microbial polyphosphate system for enhancing plant phosphate uptake and growth under nutrient-limited conditions

Overview

Phosphorus is an essential macronutrient for plant growth, yet low bioavailability of inorganic phosphate (Pi) in soils severely limits crop yield worldwide. This research addresses a critical agricultural challenge by developing a dual-strategy biotechnology solution to enhance plant phosphate acquisition and reduce dependence on chemical phosphate fertilizers.

The first strategy involves engineering plants with microbial polyphosphate (polyP) metabolizing enzymes—specifically polyphosphate kinase (PPK) and exopolyphosphatase (PPX) from E. coli—to create supplementary intracellular phosphate reserves. The second strategy leverages the beneficial plant-associated microbe Azospirillum brasilense, which naturally stores phosphate as polyP and promotes root development. By combining these complementary approaches, the technology aims to improve plant performance under Pi-limiting conditions.

This innovation has significant implications for sustainable agriculture, potentially reducing chemical fertilizer inputs, lowering production costs for farmers, and supporting crop resilience in phosphorus-deficient soils.

Technical specifications

Key features:

• Introduction of E. coli PPK and PPX genes into plants to enhance cellular polyphosphate metabolism and create phosphate reserves
• Transient expression of GFP-tagged PPK and PPX fusions confirmed successful protein localization in plant cells
• Interaction with Azospirillum brasilense wild-type strains demonstrated increased root hair proliferation in Arabidopsis, indicating enhanced nutrient acquisition capacity
• Planned use of CRISPR interference (CRISPRi) to down-regulate ppk and ppx genes in A. brasilense, enabling comparative studies of microbial phosphate contribution
• Testing under three growth conditions: Pi-replete, Pi-limiting, and Pi-replete followed by Pi-limiting, to assess stress resilience
• Monitoring of morphological changes, low-Pi stress marker gene expression, and quantification of Pi and polyP accumulation in plant tissues

Technology readiness level

This research is currently at an early-to-mid stage of development (TRL 3–4). Proof-of-concept has been established through successful cloning and transient expression of PPK and PPX genes in tobacco with confirmed subcellular localization. Preliminary validation with Arabidopsis inoculated with wild-type A. brasilense has shown increased root hair proliferation.

Future validation will generate homozygous transgenic Arabidopsis lines expressing PPK1 alone and both PPK1 and PPX genes, followed by comprehensive testing under varying phosphate conditions. Additionally, CRISPRi-modified A. brasilense strains will be developed to dissect the microbial contribution to plant phosphate enhancement. The research is positioned to advance toward greenhouse and field validation, with potential applications in crop improvement for sustainable agriculture.