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.

中文翻译：

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在结构上不同的cupuassu几丁质酶和渗透素参与植物对真菌Moniliophthora perniciosa的抗性。

库比苏树（Theobroma grandiflorum）对巴西具有重要的经济意义，主要是因为其浆粕和种子用于食品工业。然而，由于真菌Moniliophthora perniciosa引起的女巫扫帚疾病威胁着cupuassu水果的生产。作为其防御机制的组成部分，植物可以产生并积累与病程相关的（PR）蛋白，例如几丁质酶和渗透素。在这里，我们从cupuassu-M中鉴定了三种cupuassu PR蛋白（TgPR3，TgPR5和TgPR8）。多年生动物相互作用RNA-seq数据。TgPR3和TgPR8对应于几丁质酶，TgPR5对应于渗透素。它们与可可和涉及生物和非生物胁迫的拟南芥PR序列在系统发育上相关。通过同源性建模获得了TgPR蛋白的三维结构，几丁质和壳聚糖的分子对接表明TgPR蛋白可以与两个细胞壁分子相互作用，并且对壳聚糖具有更高的亲和力。通过RT-qPCR分析感染后8、24、48和72小时（hai）感染过多年生支原体的耐药和易感铜绿型基因型的TgPR基因表达。与易感植物相比，TgPR基因在抗性植物中表达更高，主要是在8和24海里的TgPR5表达，而在易感铜绿植物中表达则较低。据我们所知，这是cupuassu PR蛋白的首次计算机和体外报道。数据表明，TgPRs可能通过几丁质受体参与植物先天免疫系统的识别机制。我们的结果还表明，几丁质酶/壳聚糖酶对TgPR5 /渗透蛋白的假定作用。