Accumulation of Phosphorus-Containing Compounds in Developing Seeds of Low-Phytate Pea (Pisum sativum L.) Mutants.

Arun S K Shunmugam,Gordon R Gray,Cheryl Bock,Thomas D Warkentin,Fawzy Georges,Gene C Arganosa

doi:10.3390/plants4010001

Abstract

Low phytic acid (lpa) crops are low in phytic acid and high in inorganic phosphorus (Pi). In this study, two lpa pea genotypes, 1-150-81, 1-2347-144, and their progenitor CDC Bronco were grown in field trials for two years. The lpa genotypes were lower in IP6 and higher in Pi when compared to CDC Bronco. The total P concentration was similar in lpa genotypes and CDC Bronco throughout the seed development. The action of myo-inositol phosphate synthase (MIPS) (EC 5.5.1.4) is the first and rate-limiting step in the phytic acid biosynthesis pathway. Aiming at understanding the genetic basis of the lpa mutation in the pea, a 1530 bp open reading frame of MIPS was amplified from CDC Bronco and the lpa genotypes. Sequencing results showed no difference in coding sequence in MIPS between CDC Bronco and lpa genotypes. Transcription levels of MIPS were relatively lower at 49 days after flowering (DAF) than at 14 DAF for CDC Bronco and lpa lines. This study elucidated the rate and accumulation of phosphorus compounds in lpa genotypes. The data also demonstrated that mutation in MIPS was not responsible for the lpa trait in these pea lines.

Highlights

Phytic acid is the major storage form of phosphorus (P) in most plant seeds [1]
We examined myo-inositol phosphate synthase (MIPS) gene expression and analyzed the sequence at the nucleotide and protein levels to ascertain if variation in MIPS coding sequences was responsible for the lpa trait
The agronomic characteristics of the lpa pea genotypes were similar to their normal phytate progenitor CDC Bronco except for 1000 seed weight and grain yield at maturity (Figure 1, Table 1)

Summary

Introduction

Phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate; IP6) is the major storage form of phosphorus (P) in most plant seeds [1]. Endogenous phytase enzymes break down phytate during seed germination and release its phosphorus, myo-inositol, and mineral contents for use by the growing seedling [4]. IP6 accumulates in other plant tissues and organs that accumulate nutrient stores for subsequent redistribution, such as pollen, roots, and tubers [5]. Applied interest in seed IP6 primarily concerns its roles in human health and animal nutrition. It is a strong chelator of mineral elements such as iron, zinc, calcium, and potassium, forming mixed salts that are largely excreted by humans and other non-ruminant animals such as poultry, swine, and fish [6,7]

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