Involvement of structurally distinct cupuassu chitinases and osmotin in plant resistance to the fungus Moniliophthora perniciosa

• Published in: Plant physiology and biochemistry Vol. 148; pp. 142 - 151
• Main Authors: Santana Silva, Raner José, Alves, Rafael Moyses, Peres Gramacho, Karina, Marcellino, Lucilia Helena, Micheli, Fabienne
• Format: Journal Article
• Language: English
• Published: France Elsevier Masson SAS 01-03-2020; Elsevier
• Subjects: Agaricales - physiology; Brazil; Cacao - enzymology; Cacao - microbiology; Chitin; Chitinases - chemistry; Chitinases - metabolism; Chitosan; Disease Resistance; Gene expression; Life Sciences; Molecular docking; Molecular Docking Simulation; Pathogenesis-related proteins; Plant Proteins - chemistry; Plant Proteins - metabolism; Vegetal Biology; Witches' broom disease; Brazil; 3D; PAMP; Pathogenesis-related proteins; PR; Witches' broom disease; TLP; Chitin; Chitosan; Gene expression; Molecular docking
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2020.01.009

The cupuassu tree (Theobroma grandiflorum) is a crop of great economic importance to Brazil, mainly for its pulp and seeds, which are used in food industry. However, cupuassu fruit production is threatened by witches' broom disease caused by the fungus Moniliophthora perniciosa. As elements of its defense mechanisms, the plant can produce and accumulate pathogenesis-related (PR) proteins such as chitinases and osmotins. Here, we identified three cupuassu PR proteins (TgPR3, TgPR5 and TgPR8) from cupuassu-M. perniciosa interaction RNA-seq data. TgPR3 and TgPR8 corresponded to chitinases, and TgPR5 to osmotin; they are phylogenetically related to cacao and to Arabidopsis PR sequences involved in biotic and abiotic stress. The TgPR proteins' tridimensional structure was obtained through homology modeling, and molecular docking with chitin and chitosan showed that the TgPR proteins can interact with both cell wall molecules and presented a higher affinity for chitosan. TgPR gene expression was analyzed by RT-qPCR on resistant and susceptible cupuassu genotypes infected by M. perniciosa at 8, 24, 48 and 72 h after infection (hai). The TgPR genes showed higher expression in resistant plants compared to the susceptible ones, mainly for TgPR5 at 8 and 24 hai, while the expression was lower in the susceptible cupuassu plants. To our knowledge, this is the first in silico and in vitro reports of cupuassu PR protein. The data suggested that TgPRs could be involved in recognizing mechanisms of the plant's innate immune system through chitin receptors. Our results also suggest a putative role of chitinase/chitosanase for the TgPR5/osmotin.
•TgPRs are chitinases and osmotine with distinct 3D structures.•TgPRs interacted with chitin and chitosan, having higher affinity energy to chitosan.•The osmotine TgPR5 may act as chitinase/chitosanase.•TgPRs were highly expressed in resistant cupuassu infected by Moniliphthora perniciosa.•TgPR may participate to the cupuassu innate immune system in the early interaction stage.