Analysis of nucleotide sequences and expression levels of the ABI3 and FUS3 genes in Pisum sativum L. genotypes differs in seed storage protein content

Pea (Pisum sativum L.) is an important high-protein crop that is grown in large areas in many temperate regions of the world. However, the molecular markers of the high content of seed storage proteins in pea remain unknown. The aim of our study was to sequence the genes of transcription factors ABI3 and FUS3 and analyze their expression levels in two groups of pea cultivars and lines, contrastingly differing in seed protein content, in the conditions of the Pre-Ural forest-steppe zone in Russia. By analyzing the seed protein content of 110 cultivars and lines, 12 samples with high protein content (23.5–26.1%) and 10 samples with low protein content (18.0–19.7%) were selected. Three nucleotide substitutions were identified in the ABI3 gene that may be associated with protein accumulation in seeds: 1047 bp (T/C), 1194 bp (C/T), and 1334 bp (A/T), but only the last one resulted in an amino acid substitution in the predicted protein molecule. Three substitutions were also identified in the FUS3 gene that may be associated with protein accumulation in seeds: 669 bp (T/G), 681 bp (T/C), and 996 bp (A/C), but none of these resulted in amino acid substitutions. The expression levels of ABI3 (PsABI3-5, PsABI3-6 isoforms) and FUS3 genes at all stages of seed development depended on the genotype. No correlation between the expression levels of these genes and protein content in seeds could be detected.