Red Walnut: Characterization of the Phenolic Profiles, Activities and Gene Expression of Selected Enzymes Related to the Phenylpropanoid Pathway in Pellicle during Walnut Development

Abstract

A rare walnut variant with a red seed coat (pellicle) was examined for alterations in its phenolic profile during development. The red-walnut (RW) pellicle was compared with two commonly colored walnut varieties: 'Lara' (brown) and 'Fernor' (light brown). Furthermore, the activities of selected enzymes of the phenylpropanoid- and flavonoid-related pathways and the relative expressions of the structural genes phenylalanine ammonia lyase ( PAL) and anthocyanidin synthase ( ANS) were examined in the pellicles of the three varieties. In the pellicles of the RWs, phenylalanine ammonia lyase (PAL) activity and related PAL expression was most pronounced in August, about one month before commercial maturity, suggesting a high synthesis rate of phenolic compounds at this development stage. The most pronounced differences between the red and light- and dark-brown varieties were the increased PAL activity, PAL expression, and ANS expression in RWs in August. The vibrant color of the RW pellicle is based on the presence of four derivatives of cyanidin- and delphinidin-hexosides.

Transcriptome profiling for pericarp browning during long-term storage of intact lotus root (Nelumbo nucifera)

“…Several genes related to SM showed differential expressions when lotus root was subjected to long-term storage (e.g., those related to PAL, POD, 4CL, CHS, CSE, and COMT; Table 1: S7), which suggested that high SM-related gene expressions promoted the activity of relevant enzymes leading to an increase in phenolic compounds derived from the phenylpropanoid pathway. This result is consistent with other studies on browning in fresh-cut fruits and vegetables (Hisaminato et al 2014;Persic 2018;Liu et al 2018). Furthermore, a number of lipid and membrane related DEGs identified by the GO distribution encoded key enzymes involved in fatty acid biosynthesis and the lipid degradation pathways (Table 1; Fig.…”

Genome-Wide Identification and Transcriptional Expression of the PAL Gene Family in Common Walnut (Juglans Regia L.)

“…Transcription analysis revealed that JrPAL was expressed in all tested tissues including roots, stems, and leaves, with the highest transcription level found in roots [31]. From June to September, the related JrPAL expression was most pronounced in August, indicating a high synthesis rate of phenolic compounds at this development stage in different varieties of J. regia [33]. In black walnut ( J. nigra ), PAL genes were also strongly expressed in autumn, suggesting that their transcription in these tissues contributes to phenolic biosynthesis [34].…”

Phenolic profiles of quince (Cydonia oblonga Mill.) leaf extracts obtained by different extraction methods

“…After various extraction procedures, the samples were centrifuged and filtrated through 0.20 μm Chromafil AO-20/25 polyamide filters (Macherey-Nagel, Düren, Germany) into vials. The samples were further analyzed by the protocol described in Persic et al (2018). The determination of individual phenolics was carried out on a Thermo Finnigan Surveyor high-performance liquid chromatography system (HPLC, Thermo Fisher Scientific, Waltham, USA).…”