The gibberellin GID1-DELLA signalling module exists in evolutionarily ancient conifers

Ran Du,Yang Liu,Xinrui Sun,Wei Li,Ilga Porth,Shihui Niu,Yousry A. El-Kassaby

doi:10.1038/s41598-017-11859-w

Abstract

Gibberellins (GAs) participate in controlling various aspects of basic plant growth responses. With the exception of bryophytes, GA signalling in land plants, such as lycophytes, ferns and angiosperms, is mediated via GIBBERELLIN-INSENSITIVE DWARF1 (GID1) and DELLA proteins. To explore whether this GID1-DELLA mechanism is present in pines, we cloned an orthologue (PtGID1) of Arabidopsis AtGID1a and two putative DELLA proteins (PtDPL; PtRGA) from Pinus tabuliformis, a widespread indigenous conifer species in China, and studied their recombinant proteins. PtGID1 shares with AtGID1a the conserved HSL motifs for GA binding and an N-terminal feature that are essential for interaction with DELLA proteins. Indeed, A. thaliana 35S:PtGID1 overexpressors showed a strong GA-hypersensitive phenotype compared to the wild type. Interactions between PtGID1 and PtDELLAs, but also interactions between the conifer-angiosperm counterparts (i.e. between AtGID1 and PtDELLAs and between PtGID1 and AtDELLA), were detected in vivo. This demonstrates that pine has functional GID1-DELLA components. The Δ17-domains within PtDPL and PtRGA were identified as potential interaction sites within PtDELLAs. Our results show that PtGID1 has the ability to interact with DELLA and functions as a GA receptor. Thus, a GA-GID1-DELLA signalling module also operates in evolutionarily ancient conifers.

Highlights

Gibberellins (GAs) are a class of phytohormones that function in a wide range of basic plant growth responses
Homology modelling for PtGID1 further showed that the PtGID1 core domain is similar to that of OsGID1 based on crystal structure-derived information for the rice orthologue (Figure S2)
We cloned five sequences from P. tabuliformis that had high sequence homology to GIBBERELLIN-INSENSITIVE DWARF1 (GID1) proteins, and confirmed that only PtGID1 is orthologous to the A. thaliana and rice GID1 genes

Summary

Introduction

Gibberellins (GAs) are a class of phytohormones that function in a wide range of basic plant growth responses. Angiosperms use the GA-GID1 (GIBBERELLIN-INSENSITIVE DWARF1)-DELLA pathway, which involves the nuclear GA receptor GID18, the repressor DELLA protein[9,10], and the F-box protein GID2/SLY1, which degrades the repressor DELLA protein to trigger GA-mediated downstream responses[5,11,12]. It has not yet been thoroughly studied, GA signalling in conifers should follow the GID1-DELLA pathway; this molecule is present in early vascular plants such as the lycophyte Selaginella moellendorffii[13], but not in non-vascular bryophytes[14]. A 17-amino-acid deletion(Δ17), DELLAVLGYKVRSSEMA, within the DELLA region turns proteins into constitutive repressors of GA signalling, wherein DELLA fails to interact with GID1 in the presence of GA, conferring a GA-insensitive dwarf phenotype[9,23]

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Results

Conclusion