Molecular Characterization and Expression Patterns of the HkSVP Gene Reveal Distinct Roles in Inflorescence Structure and Floral Organ Development in Hemerocallis fulva.

Yingzhu Liu,Qixiang Zhang,Lin Yuan,Yike Gao

doi:10.3390/ijms222112010

Abstract

SHORT VEGETATIVE PHASE (SVP) genes are members of the well-known MADS-box gene family that play a key role in regulating vital developmental processes in plants. Hemerocallis are perennial herbs that exhibit continuous flowering development and have been extensively used in landscaping. However, there are few reports on the regulatory mechanism of flowering in Hemerocallis. To better understand the molecular basis of floral formation of Hemerocallis, we identified and characterized the SVP-like gene HkSVP from the Hemerocallis cultivar ‘Kanai Sensei’. Quantitative RT-PCR (qRT-PCR) indicated that HkSVP transcript was mainly expressed in the vegetative growth stage and had the highest expression in leaves, low expression in petals, pedicels and fruits, and no expression in pistils. The HkSVP encoded protein was localized in the nucleus of Arabidopsis protoplasts and the nucleus of onion epidermal cells. Yeast two hybrid assay revealed that HKSVP interacted with Hemerocallis AP1 and TFL1. Moreover, overexpression of HkSVP in Arabidopsis resulted in delayed flowering and abnormal phenotypes, including enriched trichomes, increased basal inflorescence branches and inhibition of inflorescence formation. These observations suggest that the HkSVP gene may play an important role in maintaining vegetative growth by participating in the construction of inflorescence structure and the development of flower organs.

Highlights

The transition from vegetative to reproductive growth is a major developmental switch in the life cycle of plants and is required for successful sexual reproduction of flowering plants
SHORT VEGETATIVE PHASE (SVP), which encodes a MADS-box transcription factor that represses the FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) floral pathways to suppress the transition of reproductive development, could be involved in maintenance of the plant vegetative growth period and determination of the specificity of the flower meristem [6,7,8,9,10]
It has been reported that ectopic overexpression of SVP in transgenic Arabidopsis svp mutants leads to the formation of bud-like structures and leaflike sepals instead of flowers [10,18], causes floral defects including delayed flowering in wild type (WT) Arabidopsis [18], and inhibits early transition and prolonged co-florescence development in tobacco [9]. These results suggest that plants have evolved diversified SVPs to address changes in species and environmental stress in terms of their roles in determining the vegetative phase and floral transition [12]

Summary

Introduction

The transition from vegetative to reproductive growth is a major developmental switch in the life cycle of plants and is required for successful sexual reproduction of flowering plants. This process is controlled by environmental stimuli signals and the complex internal genetic network [1,2]. SHORT VEGETATIVE PHASE (SVP), which encodes a MADS-box transcription factor that represses the FT and SOC1 floral pathways to suppress the transition of reproductive development, could be involved in maintenance of the plant vegetative growth period and determination of the specificity of the flower meristem [6,7,8,9,10]. SVP acts redundantly and directly to interact with TERMINAL FLOWER1 (TFL1)

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Conclusion