The study shows that two tobacco transcription factors, NtMYC2a and NtMYC2b, act as positive regulators of ABA-mediated seed germination by activating NtABI5, a key ABA-response gene. When both NtMYC2 genes were knocked out, tobacco seeds became less sensitive to ABA and germinated more readily; when either gene was overexpressed, seeds became more ABA-sensitive and germinated less efficiently.
Seed germination is a critical developmental switch in plants, determining whether seeds remain dormant or begin growth when environmental conditions are suitable. Current research has shown that this transition is controlled by both external cues, such as light, temperature, nitrate, and moisture, and internal hormonal signals, especially the antagonistic balance between ABA and gibberellin. ABA promotes dormancy and delays germination through a signaling pathway involving receptors, protein phosphatases, kinases, and downstream transcription factors such as ABI5. Although MYC2 transcription factors are known to regulate jasmonate signaling, nicotine biosynthesis, stress responses, and pollen development in tobacco, their role in ABA-mediated seed germination has remained unclear. This knowledge gap has limited understanding of how tobacco seeds integrate hormonal signals at the transcriptional level.
A study (DOI:10.48130/seedbio-0026-0008) published in Seed Biology on 13 April 2026 by Ligang Chen’s team, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, reports that NtMYC2a and NtMYC2b interact with each other and synergistically activate NtABI5 expression, thereby positively regulating ABA-mediated seed germination in tobacco.
To investigate this mechanism, the researchers first examined how NtMYC2a and NtMYC2b respond to ABA treatment. Reverse transcription quantitative polymerase chain reaction and western blotting showed that ABA reduced both transcript and protein levels of the two transcription factors, suggesting their involvement in ABA signaling. The team then compared wild-type tobacco seeds with Ntmyc2a, Ntmyc2b, and Ntmyc2a/2b mutant seeds on media containing different ABA concentrations. Under normal conditions, the mutant and wild-type seeds showed no major phenotypic differences. Under ABA treatment, however, the double mutant seeds germinated more readily and showed stronger cotyledon greening than wild-type seeds, indicating reduced ABA sensitivity. In contrast, tobacco lines overexpressing NtMYC2a or NtMYC2b showed lower germination and greening rates under ABA, confirming that these genes enhance ABA responsiveness. The researchers next tested whether NtMYC2a and NtMYC2b influence ABA-related genes. Gene expression analysis showed that NtABI3 and NtABI5 were reduced in the double mutant but increased in overexpression lines. Because a G-box element was found in the NtABI5 promoter, the team used electrophoretic mobility shift assays to determine whether the NtMYC2 proteins directly bind this promoter region. The results confirmed specific binding to the G-box. Transient dual-luciferase reporter assays in Nicotiana benthamiana leaves further showed that both NtMYC2a and NtMYC2b activate NtABI5 expression. Finally, AlphaFold-based interaction prediction, pull-down assays, and split-luciferase complementation demonstrated that NtMYC2a and NtMYC2b physically interact, forming a heterodimer that activates NtABI5 more strongly than either factor alone.
Together, the study reveals NtMYC2a and NtMYC2b as important upstream regulators of NtABI5 in tobacco seed germination. By clarifying how these transcription factors connect ABA signaling with germination control, the work expands understanding of MYC2 functions beyond jasmonate-related pathways and nicotine metabolism. The findings also suggest that fine-tuning MYC2-mediated ABA responses could become a useful direction for improving seed performance, stress adaptation, and early seedling establishment in tobacco and potentially other crops.
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References
DOI
10.48130/seedbio-0026-0008
Original Source URL
https://doi.org/10.48130/seedbio-0026-0008
About Seed Biology
Seed Biology (e-ISSN 2834-5495) is published by Maximum Academic Press in partnership with Yazhou Bay Seed Laboratory. Seed Biology is an open access, online-only journal focusing on research related to all aspects of the biology of seeds, including but not limited to: evolution of seeds; developmental processes including sporogenesis and gametogenesis, pollination and fertilization; apomixis and artificial seed technologies; regulation and manipulation of seed yield; nutrition and health-related quality of the endosperm, cotyledons, and the seed coat; seed dormancy and germination; seed interactions with the biotic and abiotic environment; and roles of seeds in fruit development. Seed biology publishes a wide range of research approaches, such as omics, genetics, biotechnology, genome editing, cellular and molecular biology, physiology, and environmental biology. Seed Biology publishes high-quality original research, reviews, perspectives, and opinions in open access mode, promoting fast submission, review, and dissemination freely to the global research community.