Auxin and Its Interaction With Ethylene Control Adventitious Root Formation and Development in Apple Rootstock

Abstract

Adventitious root (AR) formation is indispensable for vegetative asexual propagation. Indole-3-butyric acid (IBA) functioned indirectly as precursor of IAA in regulating AR formation. Ethylene affects auxin synthesis, transport, and/or signaling processes. However, the interactions between auxin and ethylene that control AR formation in apple have not been elucidated. In this study, we investigated the effects of IBA and its interaction with ethylene on AR development in apple. The results revealed that IBA stimulated the formation of root primordia, increased the number of ARs, and upregulated expression of genes (MdWOX11, MdLBD16, and MdLBD29) involved in AR formation. Comparison of different periods of IBA application indicated that IBA was necessary for root primordium formation, while long time IBA treatment obviously inhibited root elongation. RNA-seq analysis revealed that many plant hormone metabolism and signal transduction related genes were differentially expressed. IBA stimulated the production of ethylene during AR formation. Auxin inhibiting ARs elongation depended on ethylene. Together, our results suggest that the inhibitory role of auxin on AR elongation in apples is partially mediated by stimulated ethylene production.

Exogenous hormones supplementation improve adventitious root formation in woody plants

“…The dash lines represent the endogenous hormone response to exogenous hormone application. Green letters represent references 1–10: 1) Ford et al (2002) ; 2) de Almeida et al (2015) ; 3) de Almeida et al (2015) ; 4) Fett-Neto et al (2001) ; 5) Harfouche et al (2007) ; 6) Liu et al (2021) ; 7) Liu et al (2021) ; 8) Bai et al (2020) ; 9) Kilkenny et al (2012) ; 10) Munir et al (2021) . The arrows and “T” at the end of lines represent positive and negative regulation, respectively.…”

“…In apple ( Malus domestica Borkh.) propagation, the rooting rate in cutting is significantly higher after treatment under 3 g/L IBA with 50 mM H 2 O 2 since H 2 O 2 significantly enhances the effect of IBA on rooting ( Xiao et al, 2014 ), or only with 3 g/L IBA ( Li X et al, 2021 ) for 1 min and then inserted into fine sand and incubated in a mist solar greenhouse, and study has demonstrated that IBA stimulates the production of Eth to stimulate AR formation in apple rootstock propagation ( Bai et al, 2020 ; Devi et al, 2021 ). Olive is one of the hard-to-rooting plants, the hardwood cuttings of olive ( Olea europaea ‘Manzanilla') treated under 3 g/L IBA showed a 1.8-fold increase in rooting rate ( Khajehpour et al, 2014 ).…”

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

“…Our previous studies have demonstrated that 10 μM ETH could significantly induce adventitious root development in cucumber and marigold ( Tagetes erecta L.) [ 1 , 15 , 16 ]. Moreover, ETH is associated with other signal molecules, such as nitric oxide (NO), auxin, and calcium ions (Ca 2+ ) in the promotion of adventitious rooting [ 1 , 8 , 17 , 18 ]. For example, NO could be involved in ETH-promoting adventitious root development by enhancing the activities of nitric oxide synthase (NOS) and nitrate reductase (NR), and by regulating rooting-related genes [ CsDNAJ-1 and calcium-dependent protein kinases 1/5 ( CsCDPK1/5) ] [ 1 ].…”

“…rootstock by regulating ETH synthesis. Both auxin and ETH inhibitors significantly prevented adventitious rooting in apple [ 17 ]. Auxin increased the transcript levels of ETH biosynthesis genes, including 1-aminocyclopropane-l-carboxylic acid synthase (ACS) and ACC oxidase (ACO), which resulted in the retention of ETH [ 8 ].…”

The Involvement of Glucose in Hydrogen Gas-Medicated Adventitious Rooting in Cucumber

“…Normally, inappropriate conditions including injury and stress promote AR formation. Recent results revealed that AR formation was positively regulated by plant hormones and signaling molecules, such as abscisic acid (ABA) [ 2 ], auxin [ 3 ], brassinolide (BR) [ 4 ], gibberellin (GA) [ 5 ], ethylene [ 6 ], hydrogen peroxide (H 2 O 2 ) [ 7 ], nitric oxide (NO) [ 8 ], carbon monoxide (CO) [ 9 ] and hydrogen sulfide (H 2 S) [ 10 ] Additionally, molecular evidence illustrated that auxin- and ethylene-related genes and proteins are closely associated with the initiation and development of AR [ 11 ]. The complex responses regulated by these hormones, signaling molecules, genes and proteins are most likely to be achieved by a more detailed AR signaling process.…”