Pichia galeiformis Induces Resistance in Postharvest Citrus by Activating the Phenylpropanoid Biosynthesis Pathway

Abstract

This study aimed to investigate the effect of Pichia galeiformis on disease resistance and elucidate the changes in phenylpropane biosynthesis treated by P. galeiformis in postharvest citrus. The results showed that P. galeiformis reduced the disease incidence and lesion diameters without direct contact with the pathogen Penicillium digitatum. Transcriptome analysis revealed that phenylpropanoid biosynthesis was triggered by P. galeiformis. Genes encoding phenylpropanoid biosynthesis were upregulated, including phenylalanine ammonia-lyase (PAL), 4-coumaroyl-CoA ligase (4CL), cinnamate-4-hydroxylase (C4H), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD), O-methyltransferase, and hydroxyl cinnamoyl transferase. Moreover, P. galeiformis increased the activity of PAL, 4CL, C4H, POD, polyphenol oxidase, and CAD in citrus pericarp. In addition, P. galeiformis treated citrus displayed higher levels of total phenolic compounds, flavonoid, and lignin and higher amounts of ferulic and sinapic acid. In conclusion, these results suggested that P. galeiformis could induce resistance through modulating the pathway of phenylpropanoid biosynthesis in postharvest citrus.

Albedo- and Flavedo-Specific Transcriptome Profiling Related to Penicillium digitatum Infection in Citrus Fruit

“…The results presented herein also highlight the greater relevance of not only the ERF TFs, which may be key regulators of symptomatic versus asymptomatic signaling during necrotrophic fungal colonization [ 35 ], but also of the WRKY and MYB transcriptional regulators in flavedo ( Figure 4 B). The up-regulation of different TFs during the elicitation of resistance against P. digitatum has been shown [ 12 ], but their function in citrus fruit immunity against P. digitatum is still practically unknown. However, a recent report has shown that the overexpression of CsWRKY65 , which was more expressed in flavedo at fruit harvest, favors ROS accumulation and PR gene expression [ 36 ].…”

“…The up-regulation in both tissues of cytochrome CYP706A4 is also remarkable ( Supplementary Material Table S4 ), which is responsible for the biosynthesis of amino acids and downstream derivatives, as is the CYP75B1 flavonoid 3′-hydroxylase, which participates in the elicited resistance against this pathogen [ 10 , 12 , 16 ]. Lastly, the most specific gene induced in flavedo with a 17.9-fold increase was a ZIP TF showing homology to an Arabidopsis gene involved in callose metabolism regulation, which further suggests the relevance of cell wall reinforcement in flavedo to cope with P. digitatum infection.…”

“…Transcriptomic studies that focus on either analyzing molecular responses to P. digitatum [ 5 , 8 ] or mechanisms related to the elicitation of resistance [ 10 , 11 , 12 , 13 ] have been performed in recent years on citrus fruit peel. Yet, despite the inner peel part (albedo) being more susceptible to P. digitatum infection than the outer colored part (flavedo) [ 14 ], and both the composition and morphology of both peel tissue differing [ 15 , 16 ], no information about the different responses of each specific peel tissue to the pathogen is available.…”

Dynamic variation of the phytochemical and volatile compounds in the pericarp ofCitrus reticulata‘‘Chachi’’ (Rutaceae) during 2 years of storage

“…In this experiment, the same batch of CRCP was used to observe the dynamic changes during 2 years of storage in the same environment, of which the results indicated that the contents of TFs and TPAs decreased. Chen et al (2021) have illustrated that the phenylalanine ammonia-lyase (PAL) is the major rate-limiting enzyme for the synthesis of flavonoids. In addition, the polyphenol oxidase (PPO) plays an important role in the oxidation of phenols into quinone compounds (Habibi et al, 2020).…”

Phenylalanine, Tyrosine, and DOPA Are bona fide Substrates for Bambusa oldhamii BoPAL4

“…Phenylalanine ammonia-lyase (PAL, EC 4.3.1.24) is the enzyme that catalyzes the first committed step of general phenylpropanoid pathways in plants, catalyzing the conversion of L-phenylalanine (L-Phe) to trans-cinnamic acid via a non-oxidative deamination reaction (Scheme 1) [1][2][3]. Trans-cinnamic acid served as the start point of secondary metabolism is then hydroxylated by a membrane-bounded cinnamate 4-hydroxylase (C4H, EC 1.14.14.91) to yield p-coumaric acid [4] for the synthesis of thousands of phenylpropanoids [5,6]. Plant hormone, salicylic acid, is also synthesized via the PAL-mediated pathway [7].…”