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Gibberellins and light synergistically promote somatic embryogenesis from the in vitro apical root sections of spinach

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Abstract

Gibberellins (GAs) play a pivotal role in the induction of somatic embryogenesis from in vitro root apices of spinach plants. With the aim to understand the role of GAs in this process and to improve somatic embryo (SE) regeneration efficiency, the impact of light and GAs on SE initiation from the in vitro root apices was studied. The root sections were isolated from in vitro-grown SE-derived plants and placed on medium containing 20 µM α-naphthaleneacetic acid (NAA) and 0–10 µM GA3 or GA1, and cultivated under light conditions or in darkness. The most efficient SE regeneration response (100% regenerating SEs and 40.73 SEs per root apices) was achieved only in the presence of both light and GAs, with GA3 always exhibiting much stronger effect than GA1. Considering that light enhances GAs biosynthesis and the necessity of GAs for SE initiation, the expression levels of genes encoding the key enzymes involved in the final steps of GAs synthesis (SoGA20-ox1 and SoGA3-ox1) and deactivation (SoGA2-ox1, SoGA2-ox2 and SoGA2-ox3) were analyzed. Light enhanced the expression of all five GA-ox genes, while exogenously supplied NAA + GA3 provoked downregulation of SoGA20-ox1 and SoGA3-ox1 and upregulation of SoGA2ox-2 and SoGA2ox-3 expression. The expression of SoGA2ox-1 only slightly decreased. The results indicated the capability of isolated spinach roots to perceive the light and autonomously produce GAs. The expression levels of genes encoding key enzymes involved in GA biosynthesis suggest that lower levels of GAs favor SE initiation.

Key message

Light and gibberellins (GA) synergistically promote somatic embryogenesis in spinach. Expression levels of genes encoding key enzymes for GA metabolism suggest that lower levels of GAs may favor somatic embryogenesis.

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Acknowledgements

This research was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia through contract No. 173015 and a grant given to Maja Belić (former Milić, Grant No. 451-03-1629/2017/2138). The authors would like to express their gratitude to Dr R.P. Pharis for kind gift of GA1.

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JM and SZK designed the research. MB, ST, NB and JM conducted tissue culture experiments. MB and DJ conducted histological study, and MB, JS and JM performed RTqPCR analysis. MB and JM analyzed data. JM, SZK, DJ and MB wrote the manuscript and JS, ST and NB contributed to editing. All authors read and approved the final version of the manuscript.

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Correspondence to Jelena Milojević.

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Belić, M., Zdravković-Korać, S., Janošević, D. et al. Gibberellins and light synergistically promote somatic embryogenesis from the in vitro apical root sections of spinach. Plant Cell Tiss Organ Cult 142, 537–548 (2020). https://doi.org/10.1007/s11240-020-01878-3

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