Sucrose interferes with endogenous cytokinin homeostasis and expression of organogenesis-related genes during de novo shoot organogenesis in kohlrabi

Tatjana Ćosić,Jelena Savić,Marija Marković,Václav Motyka,Petre I Dobrev,Slavica Ninković,Martin Raspor

doi:10.1038/s41598-021-85932-w

Tatjana Ćosić, Jelena Savić + Show 5 more

Open Access

https://doi.org/10.1038/s41598-021-85932-w

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Abstract

Cross-talk between phytohormones and sugars is intensely involved in plant metabolism, growth and regeneration. We documented alterations in cytokinin (CK) homeostasis in four developmental stages during de novo shoot organogenesis (DNSO) of kohlrabi (Brassica oleracea var. gongylodes cv. Vienna Purple) seedlings induced by exogenous CKs, trans-zeatin (transZ) and thidiazuron (TDZ), added together with elevated sucrose concentration (6% and 9%). Significant impact of CK and sucrose treatment and their interaction was recorded in all investigated stages, including plantlet development before calli formation (T1 and T2), calli formation (T3) and shoot regeneration (T4). Results showed remarkable increase in total CK levels for transZ treatment, particularly with 9% sucrose. This trend was observed for all physiological and structural groups of CKs. Application of TDZ contributed to little or no increase in CK levels regardless of sucrose concentration. Analysis of expression profiles of organogenesis-related genes involved in auxin transport, CK response, shoot apical meristem formation and cell division revealed that higher sugar concentration significantly downregulated the analysed genes, particularly in T3. This continued on TDZ, but transZ induced an opposite effect with 9% sucrose in T4, increasing gene activity. Our results demonstrated that phytohormone metabolism might be triggered by sucrose signalling in kohlrabi DNSO.

Highlights

Cross-talk between phytohormones and sugars is intensely involved in plant metabolism, growth and regeneration
CK homeostasis of plants is much dependent on the presence of exogenous CKs in growth media[5,6], which are shown to be involved in upregulating auxin biosynthesis and transport, leading to elevation of endogenous auxin levels[6,7,8]
One of the further elements of the CK cascade that was shown to be affected by altered CK homeostasis during de novo shoot organogenesis (DNSO) due to the presence of exogenous CKs in the growth medium is the gene RGD3 (ROOT GROWTH DEFECTIVE3)[12], whose protein product is involved in controlling the development of adventitious shoot apical meristem (SAM)[13]

Summary

Introduction

Cross-talk between phytohormones and sugars is intensely involved in plant metabolism, growth and regeneration. Analysis of expression profiles of organogenesis-related genes involved in auxin transport, CK response, shoot apical meristem formation and cell division revealed that higher sugar concentration significantly downregulated the analysed genes, in T3. This continued on TDZ, but transZ induced an opposite effect with 9% sucrose in T4, increasing gene activity. CK homeostasis of plants is much dependent on the presence of exogenous CKs in growth media[5,6], which are shown to be involved in upregulating auxin biosynthesis and transport, leading to elevation of endogenous auxin levels[6,7,8] These effects could be achieved through regulating activity of auxin efflux transporters, such as PIN (PIN-FORMED) family[9]. Previous studies suggest that sugars can influence pathways activated by phytohormones through altering expression and activity of components of those pathways[20]

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