Metabolic Changes of Caffeine in Tea Plant (Camellia sinensis (L.) O. Kuntze) as Defense Response to Colletotrichum fructicola

Abstract

Tea plant (Camellia sinensis) is one of the most economically valuable crops in the world. Anthracnose can affect the growth of leaves and cause serious yield losses of tea. Tea plants are rich in secondary metabolites; however, their roles in resistance to anthracnose are unclear. Herein we compared the contents of total phenolics, catechins, and caffeine in two cultivars with different resistances to anthracnose during Colletotrichum fructicola infection. (-)-Epigallocatechin-3-gallate (EGCG), (+)-catechin (C), caffeine, and critical regulatory genes were induced in C. fructicola-resistant tissues. In vitro antifungal tests showed that caffeine more strongly inhibited mycelial growth than tea polyphenols and catechins. Both electron microscopy and bioactivity analysis results showed that caffeine can affect mycelial cell walls and plasma membranes. Through promoter sequences analysis, a number of stress response-related cis-acting elements were identified in S-adenosylmethionine synthetase and tea caffeine synthase. These results demonstrated that (-)-EGCG, (+)-C, and caffeine may be involved in the resistance of tea plants to anthracnose.

Inhibition Mechanism of Caffeine in Tea Pathogenic Fungi Botryosphaeria Dothidea and Colletotrichum Gloeosporioides

“…These ndings are in agreement with the damage observed in caffeine-treated C. fructicola [15]. Several researchers have investigated the action mechanism of caffeine against bacteria and fungi, such as affecting DNA, enzyme, and protein synthesis in bacteria [33], spore germination [34], cAMP signaling pathways [35], sugar synthesis (glucose, fructose and maltose) in mold [36] and cell walls and cell membranes [15]. However, the present study provides the rst transcriptomic analysis of the inhibition process of caffeine against the tea plant pathogenic fungi B. dothidea and C. gloeosporioides.…”

“…Zhang et al [19] noted the strong antifungal activity of caffeine (10 mg/mL) against tea foliar pathogens such as C. camelliae, P. theae and P. theicola. The MIC value of caffeine against C. fructicola was 4 mg/mL [15]. The inhibition dosage of caffeine differed between bacteria (62.5 to > 2000 µg/mL) and molds (> 5000 µg/mL) [32].…”

“…Caffeine concentration and TCS1 expression marginally increased in fungal treated susceptible and moderately resistant tea varieties and the expression of SAMS and TIDH were higher in fungal inoculated resistant tea variety. Wang et al [15] observed that number of stress response-related cis-acting elements in SAMS and TCS1 during the fungal infection and speculated that cis-acting elements activated through phytohormones and the respective genes were triggered by the fungus. So, further, we examined the expression of defense related genes involved in phenylpropanoid biosynthesis, plant hormone biosynthesis, signaling pathways and plant-pathogen interaction and other stress responsive.…”

“…The direct mechanism is observed when exogenously applied caffeine inhibits the growth and development of several organisms including bacteria, fungi and insects, and the indirect mechanism is to promote plant host's defense against pathogens [12][13][14]. Tea plant contains many secondary metabolites such as polyphenols and purine alkaloids, among them, catechins and caffeine may be involved in the tea anthracnose resistance mechanism [15]. Phenylpropanoid compounds and phytohormones played a major role against anthracnose fungus in the tea and strawberry plants, respectively [6,16].…”

“…Some bacterial species utilize caffeine for their carbon requirement, whereas other bacterial growths are arrested by caffeine [17]. Different caffeine concentrations strongly inhibited the growth of Crinipellis perniciosa and tea plant pathogenic fungi, such as Colletotrichum fructicola, C. camelliae, Pestalotiopsis theae and Phyllosticta theicola [15,18,19]. Caffeine also acts as a powerful inhibitor of cAMP phosphodiesterase in bacteria, fungi and insects [14].…”