Transcriptome and hormone Analyses reveal that melatonin promotes adventitious rooting in shaded cucumber hypocotyls

Abstract

Melatonin, a multi-regulatory molecule, stimulates root generation and regulates many aspects of plant growth and developmental processes. To gain insight into the effects of melatonin on adventitious root (AR) formation, we use cucumber seedings subjected to one of three treatments: EW (hypocotyl exposed and irrigated with water), SW (hypocotyl shaded and irrigated with water) and SM (hypocotyl shaded and irrigated with 100 µM melatonin). Under shaded conditions, melatonin induced significant AR formation in the hypocotyl. To explore the mechanism of this melatonin-induced AR formation, we used transcriptome analysis to identify 1296 significant differentially expressed genes (DEGs). Comparing SM with SW, a total of 774 genes were upregulated and 522 genes were downregulated. The DEGs were classified among different metabolic pathways, especially those connected with the synthesis of secondary metabolites, with hormone signal transduction and with plant-pathogen interactions. Analyses indicate exogenous melatonin increased contents of endogenous auxin, jasmonic acid, salicylic acid, cytokinin and abscisic acid levels during AR formation. This study indicates melatonin promotes AR formation in cucumber seedings by regulating the expressions of genes related to hormone synthesis, signaling and cell wall formation, as well as by increasing the contents of auxin, cytokinin, jasmonic acid, salicylic acid and abscisic acid. This research elucidates the molecular mechanisms of melatonin’s role in promoting AR formation in the hypocotyl of cucumber seedings under shaded conditions.

Why the adventitious roots of poplar are so colorful: RNAseq and metabolomic analysis reveal flavonols, flavones, and anthocyanins accumulation in canker pathogens-induced adventitious roots in poplar

“…were also significantly upregulated (Liu et al 2022b), suggesting a de novo biosynthesis of flavonoids and anthocyanins in duckweed variety. In our recent study, aside from gene FLS, gene PAL, CHS, CHI, F3H, DFR, ANS, LAR, and ANR are all upregulated, suggesting a de novo biosynthesis of flavonoids in the BCMV (bean common mosaic virus) infected poplar leaves (Wang et al 2023). However, one recent research illustrated that ANS genes negatively but BZ1 genes positively regulate the biosynthesis of anthocyanins in poplar 84K leaves (Yan et al 2022).…”

“…Because some SPLs also are the targets of miR156, then this microRNA can positively control the level of flavonoids/anthocyanins in citrus and switchgrass (Cai et al 2022; Feng et al 2022) and poplar (Wang et al 2020b). Our recent research also illustrated that miR156-SPL modules are involved in the biosynthesis of flavonoids or the development of mosaic symptoms in poplar-BCMV interaction (Wang et al 2023). Specifically, the expression of miR156 and a series of flavonoid/anthocyanin biosynthesis-related genes (including PAL, CHS, CHI, F3H, DFR, ANS, LAR, and ANR) were upregulated and the expression of four SPL genes (such as gene PAYG024925) were downregulated, however, none R2R3-MYB gene or “MBW” complex significant changed in the poplar mosaic leaves (Wang et al 2023).…”

“…Our recent research also illustrated that miR156-SPL modules are involved in the biosynthesis of flavonoids or the development of mosaic symptoms in poplar-BCMV interaction (Wang et al 2023). Specifically, the expression of miR156 and a series of flavonoid/anthocyanin biosynthesis-related genes (including PAL, CHS, CHI, F3H, DFR, ANS, LAR, and ANR) were upregulated and the expression of four SPL genes (such as gene PAYG024925) were downregulated, however, none R2R3-MYB gene or “MBW” complex significant changed in the poplar mosaic leaves (Wang et al 2023). Interestingly, the same SPL gene (PAYG024925), which was identified in poplar mosaic leaves, was also downregulated in the present poplar ARs (Supplementary file 9), suggesting sunlight exposure increasing the accumulation of flavonoids metabolites at the post-transcriptional level, through miR156-SPL module which increases the stability of “MBW” complex.…”

Transcriptome analysis reveals that auxin promotes strigolactone-induced adventitious root growth in the hypocotyl of melon seedlings

“…Moreover, during the formation of ARs under exogenous phytohormone treatment, a large number of genes show expression changes. Melatonin induces significant AR formation in the hypocotyl of cucumber, and 1,296 DEGs were identified by comparing ARs treated with or without melatonin using RNA-Seq analysis ( Wang et al., 2022 ). In this study, AR number, length, superficial area, and volume were increased more by the GR24+IAA treatment than by the GR24 treatment at 6–10 days, showing 1.44–1.51, 1.28–1.73, 1.19–1.83, and 1.31–1.87 times higher values, respectively.…”

“…In apple rootstock, the levels of the endogenous phytohormones indole-3-acetic acid (IAA), zeatin riboside, JA, GA, and ABA in the process of AR formation were changed, and DEGs were shown to be considerably enriched in hormone signaling-related pathways ( Tahir et al., 2021 ). Cucumber AR formation in the hypocotyl is also regulated by genes related to hormone synthesis and the AR signaling pathway ( Wang et al., 2022 ). These results prove that phytohormone synthesis and signal transduction are necessary for AR formation.…”