Abstract
Understanding phosphate uptake and storage is interesting to optimize the plant performance to phosphorus fluctuations. Phytic acid (PA) is the major source of inorganic phosphorus (Pi) in plants. Genetic analyses of PA pathway transporter genes (BnMRP5) and their functional characterization might provide clues in better utilizing the available phosphate resources. Furthermore, the failure to assimilate PA by monogastric animals results in its excess accumulation in manure, which ultimately causes groundwater eutrophication. As a first step toward breeding low PA mutants in oilseed rape (Brassica napus L.), we identified knockout mutants in PA biosynthesis and transporter genes. The obtained M3 single mutants of Bn.MRP5.A10 and Bn.MRP5.C09 were combined by crossing to produce double mutants. Simultaneously, crosses were performed with the non-mutagenized EMS donor genotype to reduce the background mutation load. Double mutants identified from the F2 progeny of direct M3 crosses and BC1 plants showed 15% reduction in PA contents with no significant differences in Pi. We are discussing the function of BnMRP5 paralogs and the benefits for breeding Bnmrp5 mutants in respect to low PA, yield, and stress tolerances.
Highlights
Phosphorus is an essential macronutrient required for plant development
Seed samples from 15, 25, 35, 45, and 55 days after pollination (DAP) were used to determine the dynamic changes of Phytic acid (PA) and Pi in developing seeds
We observed that PA was not measurable at 15 DAP, but it accumulated significantly from 15 to 35 DAP
Summary
Phosphorus is an essential macronutrient required for plant development. In plants, numerous transporters such as PHT, SPX-MFS, and phosphate antiporters facilitate the uptake of phosphorus from the soil and its mobilization across various tissues (Kopriva and Chu, 2018). The up taken phosphorus is utilized in various metabolic processes and is stored in seed vacuoles in the form of phytic acid (PA; referred as inositol hexakis phosphate), which is readily available for seedling development. Low PA mutants are desirable for a reduced application of external phosphorus in the form of fertilizers. They could help to decrease the dependency on non-renewable rock phosphates (Lott et al, 2007). In this regard, PA biosynthetic genes have been knocked out in different plant species to obtain low PA mutants with simultaneous increase of inorganic phosphorus (Pi) (Sparvoli and Cominelli, 2015).
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