Publication Date:
2019
Description:
Abstract
Crops with improved uptake of fertiliser phosphorus (P) would reduce P losses and confer environmental benefits. We examined how P‐sufficient six‐week‐old soil‐grown Trifolium subterraneum plants, and two‐week‐old seedlings in solution culture, accumulated P in roots after inorganic P (Pi) addition. In contrast to our expectation that vacuoles would accumulate excess P, after 7 d X‐ray microanalysis showed that vacuolar [P] remained low (〈12 mmol kg–1). However, in the plants after P addition some cortex cells contained globular structures extraordinarily rich in P (often 〉3000 mmol kg–1), potassium, magnesium and sodium. Similar structures were evident in seedlings, both before and after P addition, with their [P] increasing three‐fold after P addition. NMR spectroscopy showed seedling roots accumulated Pi following P addition, while TEM revealed large plastids. For seedlings we demonstrated that roots differentially expressed genes after P addition using RNAseq mapped to the T. subterraneum reference genome assembly and transcriptome profiles. Amongst the most up‐regulated genes after 4 hr was TSub_g9430.t1, which is similar to plastid envelope Pi transporters (PHT4;1, PHT4;4): expression of vacuolar Pi‐transporter homologs did not change. We suggest that subcellular P accumulation in globular structures, which may include plastids, aids cytosolic Pi homeostasis under high‐P availability.
Print ISSN:
0140-7791
Electronic ISSN:
1365-3040
Topics:
Biology
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