Identification of Key Genes during Ethylene-Induced Adventitious Root Development in Cucumber (Cucumis sativus L.)

Abstract

Ethylene (ETH), as a key plant hormone, plays critical roles in various processes of plant growth and development. ETH has been reported to induce adventitious rooting. Moreover, our previous studies have shown that exogenous ETH may induce plant adventitious root development in cucumber (Cucumis sativus L.). However, the key genes involved in this process are still unclear. To explore the key genes in ETH-induced adventitious root development, we employed a transcriptome technique and revealed 1415 differentially expressed genes (DEGs), with 687 DEGs up-regulated and 728 DEGs down-regulated. Using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, we further identified critical pathways that were involved in ETH-induced adventitious root development, including carbon metabolism (starch and sucrose metabolism, glycolysis/gluconeogenesis, citrate cycle (TCA cycle), oxidative phosphorylation, fatty acid biosynthesis, and fatty acid degradation), secondary metabolism (phenylalanine metabolism and flavonoid biosynthesis) and plant hormone signal transduction. In carbon metabolism, ETH reduced the content of sucrose, glucose, starch, the activity of sucrose synthase (SS), sucrose–phosphate synthase (SPS) and hexokinase (HK), and the expressions of CsHK2, pyruvate kinase 2 (CsPK2), and CsCYP86A1, whereas it enhanced the expressions of β-amylase 1 (CsBAM1) and β-amylase 3 (CsBAM3). In secondary metabolism, the transcript levels of phenylalanine ammonia-lyase (CsPAL) and flavonoid 3′-monooxygenase (CsF3′M) were negatively regulated, and that of primary-amine oxidase (CsPAO) was positively regulated by ETH. Additionally, the indole-3-acetic acid (IAA) content and the expressions of auxin and ETH signaling transduction-related genes (auxin transporter-like protein 5 (CsLAX5), CsGH3.17, CsSUAR50, and CsERS) were suppressed, whereas the abscisic acid (ABA) content and the expressions of ABA and BR signaling transduction-related genes (CsPYL1, CsPYL5, CsPYL8, BRI1-associated kinase 1 (CsBAK1), and CsXTH3) were promoted by ETH. Furthermore, the mRNA levels of these genes were confirmed by real-time PCR (RT-qPCR). These results indicate that genes related to carbon metabolism, secondary metabolite biosynthesis, and plant hormone signaling transduction are involved in ETH-induced adventitious root development. This work identified the key pathways and genes in ETH-induced adventitious rooting in cucumber, which may provide new insights into ETH-induced adventitious root development and will be useful for investigating the molecular roles of key genes in this process in further studies.

Time-Course Transcriptome and Phytohormonal Analysis of Blue-Light-Induced Adventitious Root Development of Tea Cuttings (Camellia sinensis (L.) Kuntze)

“…BAK1 is the receptor gene of BR, and the up-regulated expression of BAK1 can promote the root growth of Brassica napus [50], which proves that BAK1 may have a positive response to root growth. At the same time, in the study of Cucumis sativus, the upregulated expression of BAK1 had a positive regulatory effect on the adventitious root [51]. In the study of Arabidopsis, the expression of BRI1 rescued the root growth of the bri1 mutant [52,53], indicating that BRI1 was positively regulating root growth.…”

Ethylene Action Inhibition Improves Adventitious Root Induction in Adult Chestnut Tissues

“…It was described as an AR inhibitor in peach [ 35 ], Eucalyptus [ 36 ] and Malus x domestica [ 37 ]. On the other hand, there are species such as petunia [ 38 ], cucumber [ 39 ], marigold [ 40 ] and woody plants such as Pinus thunbergii [ 41 ] and Citrus sinensis [ 42 ] in which ET stimulates AR formation. However, the effect of this hormone in AR has not been analysed regarding the ontogenetic state of the tissues in woody species.…”

Key anti-freeze genes and pathways of Lanzhou lily (Lilium davidii, var. unicolor) during the seedling stage

“…In addition, under low-temperature stress, the imbalance of the light absorption capacity and light dissipation capacity of plants leads to the destruction of Photosystem II (PS II) and the inhibition of photosynthesis [ 54 ]. In low-temperature-tolerant crops, such as cucumber [ 55 ], tobacco [ 56 ], and rice [ 57 ], light intensity and ambient temperature can affect chloroplasts and initiate signal transduction at low temperatures, thus coordinating gene expression between protoplasts and nuclei to adapt to changes in ambient temperatures [ 58 ]. This result is consistent with the photosynthesis inhibition found in the transcriptome of Lanzhou lily under low-temperature stress in this experiment, indicating that Lanzhou lily can also enhance its resistance to low-temperature stress by inhibiting photosynthesis.…”