Auxin regulation and MdPIN expression during adventitious root initiation in apple cuttings

Abstract

Adventitious root (AR) formation is critical for the efficient propagation of elite horticultural and forestry crops. Despite decades of research, the cellular processes and molecular mechanisms underlying AR induction in woody plants remain obscure. We examined the details of AR formation in apple (Malus domestica) M.9 rootstock, the most widely used dwarf rootstock for intensive production, and investigated the role of polar auxin transport in postembryonic organogenesis. AR formation begins with a series of founder cell divisions and elongation of the interfascicular cambium adjacent to vascular tissues. This process is associated with a relatively high indole acetic acid (IAA) content and hydrolysis of starch grains. Exogenous auxin treatment promoted this cell division, as well as the proliferation and reorganization of the endoplasmic reticulum and Golgi membrane. In contrast, treatment with the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA) inhibited cell division in the basal region of the cuttings and resulted in abnormal cell divisions during the early stage of AR formation. In addition, PIN-FORMED (PIN) transcripts were differentially expressed throughout the whole AR development process. We also detected upregulation of MdPIN8 and MdPIN10 during induction; upregulation of MdPIN4, MdPIN5, and MdPIN8 during extension; and upregulation of all MdPINs during AR initiation. This research provides an improved understanding of the cellular and molecular underpinnings of the AR process in woody plants.

Roles of Auxin in the Growth, Development, and Stress Tolerance of Horticultural Plants

“…N-1-Naphthylphthalic acid (NPA) is an inhibitor of the polar transport of auxin. The opposite result occurred when NPA was used to treat apple cuttings, which resulted in abnormal cell divisions during the early stage of AR formation [ 31 ]. Members of the GH3 (Gretchen Hagen 3) protein family play a role in auxin homeostasis, which is an essential regulator of plant development.…”

“…MdPIN8 and MdPIN10 are up-regulated during AR induction, and MdPIN3 is up-regulated early in AR initiation, while MdPIN7 and MdPIN2 are up-regulated late in initiation, and MdPIN4 , MdPIN5 , and MdPIN8 are up-regulated during AR elongation. This suggests that different MdPIN family members may be involved in various stages of AR formation in different ways [ 31 ]. Post-translational modification of ARFs and AUX/IAAs, including phosphorylation, ubiquitination, acetylation, and SUMOylation, also significantly regulates auxin signaling.…”

Strigolactone regulates adventitious root formation via the MdSMXL7‐MdWRKY6‐MdBRC1 signaling cascade in apple

“…AR formation is an organogenesis process induced from differentiated cells of stems, leaves and hypocotyls, which can be triggered by a variety of factors, including natural growth signals and external environmental stimulations (Bellini et al., 2014). For example, mechanical damage, waterlogging, low light, soil nutrient changes and other external stimuli are all key factors for inducing rooting process (Guan et al., 2020; Jiang et al., 2022; Zhang et al., 2022).…”

Characterization of phytohormone and transcriptome profiles during protocorm-like bodies development of Paphiopedilum

“…Free IAA can be polar transported to the site of action by auxin transport carrier and participate in signal regulation. Plant-specific PIN-formed (PIN) proteins directly promote cellular auxin efflux [ 37 – 39 ]. Members of the influx carriers AUXIN RESISTANT1/ LIKE AUXIN RESISTANT (AUX1/LAX) are functional auxin influx carriers and mediate auxin-related developmental events in different organs and tissues [ 40 , 41 ].…”