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An Optimized Rhizobox Protocol to Visualize Root Growth and Responsiveness to Localized Nutrients
Published on: October 22, 2018
The NAC17-PUB30 module enhances drought stress tolerance by regulating adventitious root development in apple
Bingyang Du1, Xiang Zhang1, Yuqin Xiao1
1Frontiers Science Center for Molecular Design Breeding, College of Horticulture, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian District, Beijing 100193, China.
Abstract:
Rootstocks critically influence apple growth, development, and stress tolerance, a process likely mediated by key transcriptional regulators. Among these, NAC transcription factors are pivotal for stress responses, yet their roles in the differential drought resistance of apple rootstock varieties remain unclear. This study identified NAC transcription factor 17 (NAC17), which exhibits contrasting drought-responsive expression: it is strongly induced in drought-resistant wild apple (Malus sieversii) but remains unresponsive in drought-sensitive M26 (Malus domestica). Functional analysis demonstrated that MsNAC17 acts as a positive regulator of drought tolerance. Transgenic M26 plants overexpressing MsNAC17 showed enhanced drought resistance and promoted adventitious root development, whereas silencing MsNAC17 increased drought susceptibility. MsNAC17 directly activated the expression of LATERAL ORGAN BOUNDARIES DOMAIN 64 (MdLBD64), a key root development regulator, and MdYUCCA11, a crucial auxin biosynthesis gene. Furthermore, the E3 ubiquitin ligase Plant U-box 30 (MdPUB30) negatively regulated MsNAC17 protein stability by promoting its degradation via the ubiquitin-proteasome pathway. The differential drought responses between rootstocks were attributed to distinct upstream regulation: in M. sieversii, the transcription factor MYB47 activated MsNAC17 expression, whereas in M26, bZIP46 upregulated MdPUB30 under drought stress. These results establish the NAC17-PUB30 regulatory module as a central hub controlling drought tolerance by coordinating root architecture and auxin homeostasis, providing molecular targets for breeding drought-resistant apple rootstocks.
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