Abstract
Phytophthora root and stem rot of soybean, caused by Phytophthora sojae (P. sojae), is a destructive disease in many soybean planting regions worldwide. In a previous study, an expressed sequence tag (EST) homolog of the major allergen Pru ar 1 in apricot (Prunus armeniaca) was identified up-regulated in the highly resistant soybean ‘Suinong 10’ infected with P. sojae. Here, the full length of the EST was isolated using rapid amplification of cDNA ends (RACE). It showed the highest homolgy of 53.46% with Gly m 4 after comparison with the eight soybean allergen families reported and was named Gly m 4-like (Gly m 4l, GenBank accession no. HQ913577.1). The cDNA full length of Gly m 4l was 707 bp containing a 474 bp open reading frame encoding a polypeptide of 157 amino acids. Sequence analysis suggests that Gly m 4l contains a conserved ‘P-loop’ (phosphate-binding loop) motif at residues 47–55 aa and a Bet v 1 domain at residues 87–120 aa. The transcript abundance of Gly m 4l was significantly induced by P. sojae, salicylic acid (SA), NaCl, and also responded to methyl jasmonic acid (MeJA) and ethylene (ET). The recombinant Gly m 4l protein showed RNase activity and displayed directly antimicrobial activity that inhibited hyphal growth and reduced zoospore release in P. sojae. Further analyses showed that the RNase activity of the recombinant protein to degrading tRNA was significantly affected in the presence of zeatin. Over-expression of Gly m 4l in susceptible ‘Dongnong 50’ soybean showed enhanced resistance to P. sojae. These results indicated that Gly m 4l protein played an important role in the defense of soybean against P. sojae infection.
Highlights
Pathogenesis-related (PR) proteins were initially described as a class of plant-specific proteins that accumulated in response to pathogen infection; subsequent studies showed that these proteins are induced through a variety of biotic and abiotic stresses [1,2]
A neighbor-joining (NJ) phylogram was used to construct a phylogenetic tree based on the deduced sequence of Gly m 4l that contained other members of the PR10 family (Fig 2A), indicating that these proteins might share a common ancestor and display similar functions
The results suggested that Gly m 4l belonged to PR 10 protein family
Summary
Pathogenesis-related (PR) proteins were initially described as a class of plant-specific proteins that accumulated in response to pathogen infection; subsequent studies showed that these proteins are induced through a variety of biotic and abiotic stresses [1,2]. PR proteins are reported constitutively expressed in different tissues and organs during growth [3,4] and are currently classified into 17 functional families based on primary structure, serological relationships, and biological activities [1, 4]. Most PR proteins are localized in the vacuole extracellularly or intracellularly. PR10 proteins are intracellular and cytoplasmic [5]. Most members of the PR10 protein contain an open reading frame (ORF) of 456 to 696 nucleotides, usually interrupted by an intron of 76–359 nucleotides, which encode a polypeptide of 151–231 amino acids with predicted molecular masses of 15–26 kDa [6,7,8]. The 3D structures of PR10 proteins contain a 25-amino-acid long α-helix (α3) in C-terminal and two short α-helices (α1 and a2) in N-terminal. The α3 is surrounded by seven anti-parallel β-sheets (β1 to β7) and the α1 and α2 are located between β1 and β2 strands [9,10]
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