Phosphorus and iron defciencies induce a metabolic reprogramming and affect the exudation traits of the woody plant Fragaria×ananassa

Abstract

Strawberries are a very popular fruit among berries, for both their commercial and economic importance, but especially for their benefcial effects for human health. However, their bioactive compound content is strictly related to the nutritional status of the plant and might be affected if nutritional disorders (e.g. Fe or P shortage) occur. To overcome nutrient shortages, plants evolved different mechanisms, which often involve the release of root exudates. The biochemical and molecular mechanisms underlying root exudation and its regulation are as yet still poorly known, in particular in woody crop species. The aim of this work was therefore to characterize the pattern of root exudation of strawberry plants grown in either P or Fe defciency, by investigating metabolomic changes of root tissues and the expression of genes putatively involved in exudate extrusion. Although P and Fe defciencies differentially affected the total metabolism, some metabolites (e.g. raffnose and galactose) accumulated in roots similarly under both conditions. Moreover, P defciency specifcally affected the content of galactaric acid, malic acid, lysine, proline, and sorbitol-6-phosphate, whereas Fe defciency specifcally affected the content of sucrose, dehydroascorbic acid, galactonate, and ferulic acid. At the same time, the citrate content did not change in roots under both nutrient defciencies with respect to the control. However, a strong release of citrate was observed, and it increased signifcantly with time, being +250% and +300% higher in Fe- and P-defcient plants, respectively, compared with the control. Moreover, concomitantly, a signifcant acidifcation of the growth medium was observed in both treatments. Gene expression analyses highlighted for the frst time that at least two members of the multidrug and toxic compound extrusion (MATE) transporter family and one member of the plasma membrane H+-ATPase family are involved in the response to both P and Fe starvation in strawberry plants.