Soluble organic nutrients induce ClaPhys expression to enhance phytase activity of watermelon roots

Abstract

AbstractApplication of organic fertilisers is beneficial to the quality and yield of crops. Myo‐inositol phosphate is an abundant form of organic phosphorus (Po) in organic manure and soil, which could release phosphate (Pi) and likely be absorbed by plant after it was hydrolysed by phytase. However, whether plant roots respond to organic fertiliser to adapt myo‐inositol phosphates utilisation is not clear. Experiments were carried out to investigate the responses of phytase gene expression and enzyme activity, as well as root architecture to organic fertiliser application. The results showed that Cow‐dung‐based organic fertiliser contains 2.30 g/kg soluble P, including 0.08 g/kg myo‐inositol phosphates P. Organic acid addition promotes myo‐inositol phosphates solubility in organic fertiliser. Partial substitution of Pi with P from organic fertiliser upregulated the expression of ClaPhy1, ClaPhy2 and ClaPhy3 in roots, while it did not change ClaPHT1 family expression. Root phytase activity increased markedly at 25–30% organic fertiliser substitution rates. P concentration in watermelon leaves increased when 25% Pi was substituted with P from organic fertiliser. Organic fertiliser supply also promoted lateral root density and root hair length. In conclusion, organic fertiliser contains soluble myo‐inositol phosphates, more of which was dissolved by organic acids secreted from plant roots. Substitution of Pi with P from organic fertiliser upregulated ClaPhy genes expression and enhanced root phytase activity, as well as increased lateral root number and root hair density. Myo‐inositol phosphates hydrolysis and root morphology adaptation facilitate watermelon utilisation of myo‐inositol phosphates P in organic fertiliser. This study provides evidence to advance utilisation of myo‐inositol phosphates P from organic fertiliser by plant roots via up‐regulation of ClaPhy expression which increased phytase secretion, and optimised root morphology.