HYDERABAD: Researchers at the University of Hyderabad (UoH) have identified a protein that helps tomato plants redistribute phosphate from older leaves to younger tissues, a finding that could improve phosphate-use efficiency and help develop high-yielding crops requiring less chemical fertiliser.
Published in the Journal of Experimental Botany, the study identifies SlPAP26b, a purple acid phosphatase, as a key regulator of phosphate (Pi) remobilisation and phosphorus balance in tomato plants.
Phosphorus is vital for plant growth but can become unavailable in soil, making conventional fertilisers inefficient. Plants therefore recycle and redistribute the nutrient internally. Using an integrated omics approach, the researchers identified SlPAP26b as a key gene involved in this process. It was active in leaves and roots and particularly during leaf senescence.
The transcription factors SlPHR1 and SlPHL1 were found to directly activate SlPAP26b by binding to the P1BS element in its promoter, linking the protein to the plant’s phosphate-starvation response.
When researchers silenced SlPAP26b, plants showed reduced acid phosphatase activity and impaired phosphate movement from older to younger leaves. Radioactive phosphorus tracing confirmed lower phosphate levels in young tissues, even when plants received sufficient phosphate.
The disruption also triggered a tissue-specific phosphate-starvation response. Silencing SlPAP26b reduced SlSPX2, a negative regulator of SlPHL1, increasing SlPHL1 protein levels and activating phosphate-starvation genes in younger leaves and roots. This showed that individual tissues can respond to phosphate availability based on their access to recycled nutrients, rather than the plant’s overall phosphate status.
The researchers propose that SlPAP26b helps hydrolyse ATP and supports phosphate remobilisation from ageing leaves under normal conditions. Its suppression disrupts phosphate distribution and triggers inappropriate starvation responses.
The study was led by Prof Rahul Kumar of UoH’s Department of Plant Sciences, School of Life Sciences, and co-authored by Abhishek Roychowdhury, Akash, Rajat Srivastava and Vishal, along with researchers from Mendel University, Czech Republic, and the Spanish National Research Council (CSIC).
