PpNAC187 Enhances Lignin Synthesis in ‘Whangkeumbae’ Pear (Pyrus pyrifolia) ‘Hard-End’ Fruit

Abstract

A disorder in pears that is known as ‘hard-end’ fruit affects the appearance, edible quality, and market value of pear fruit. RNA-Seq was carried out on the calyx end of ‘Whangkeumbae’ pear fruit with and without the hard-end symptom to explore the mechanism underlying the formation of hard-end. The results indicated that the genes in the phenylpropanoid pathway affecting lignification were up-regulated in hard-end fruit. An analysis of differentially expressed genes (DEGs) identified three NAC transcription factors, and RT-qPCR analysis of PpNAC138, PpNAC186, and PpNAC187 confirmed that PpNAC187 gene expression was correlated with the hard-end disorder in pear fruit. A transient increase in PpNAC187 was observed in the calyx end of ‘Whangkeumbae’ fruit when they began to exhibit hard-end symptom. Concomitantly, the higher level of PpCCR and PpCOMT transcripts was observed, which are the key genes in lignin biosynthesis. Notably, lignin content in the stem and leaf tissues of transgenic tobacco overexpressing PpNAC187 was significantly higher than in the control plants that were transformed with an empty vector. Furthermore, transgenic tobacco overexpressing PpNAC187 had a larger number of xylem vessel elements. The results of this study confirmed that PpNAC187 functions in inducing lignification in pear fruit during the development of the hard-end disorder.

Genome-Wide Identification of NAC Transcription Factor Family in Juglans mandshurica and Their Expression Analysis during the Fruit Development and Ripening

“…In papaya (Carica papaya), CpNAC1 was reported to regulate carotenoid accumulation during fruit ripening [61]. Similar results were reported in studies on Actinidia eriantha [45], Pyrus pyrifolia [62], Malus domestica [63], Eriobotrya japonica [64], and other fruit tree species. In addition, NAC TFs also regulate fruit development and ripening through multiple hormone such as ethylene and abscisic acid biosynthesis and signal transduction pathways [65].…”

Genome-wide identification of MYB family genes potentially related to SCW biogenesis in Korla pear fruit

“…As for the rough-skinned fruits, also known as hard-end fruits in 'Whangkeumbae' pear (Pyrus pyrifolia), it is a physi-ological disorder that has become increasingly common in recent years, resulting in considerable economic loss to the pear growers. And the increased stone cell content is a main cause of hard-end disorder in pear fruits (Lu et al, 2014;Li et al, , 2019. All the SCW associated MYBs that differentially expressed in this study were abundantly expressed at the prime stage of stone cell differentiation, then expression levels started to decrease gradually.…”

Metabolome and transcriptome analysis of eleutheroside B biosynthesis pathway in Eleutherococcus senticosus

“…A total of 43 classes of TFs (140 genes) were identified in the high- and low eleutheroside B plants, including 14 NAC TFs, 9 MYB TFs, 8 MADS TFs and 8 HSF TFs were identified in the high and low eleutheroside B plants (Supplementary Figure 7; Supplementary Table 11). NAC ( Li and Cheng et al., 2019 ), MYB ( Geng et al., 2020 ), homeobox (HB) ( Testone et al., 2012 ), WRKY ( Wang et al., 2010 ); TFs are involved in the lignin synthesis regulation. The lignin and eleutheroside B biosynthetic processes belong to the phenylpropanoid metabolism and overlap between the two processes.…”