Overexpression of PIF4 affects plant morphology and accelerates reproductive phase transitions in soybean

Hina Arya,Prem L Bhalla,Mohan B Singh

doi:10.1002/fes3.291

Abstract

AbstractPhytochrome‐interacting factor 4 acts as a signalling hub for integrating multiple environmental cues like light and temperature. While the function of PIF4 in the model plant Arabidopsis has been studied, there is limited knowledge regarding the role of PIF4 in agronomically important legume crop soybean. Here, we employed a constitutive overexpression approach to functionally characterise a soybean PIF4 homolog, GmPIF4b in a determinate short‐day cultivar, Bragg. Multiple sequence alignment of seven soybean PIF4 homologs (GmPIF4a‐g) with Arabidopsis PIF4 revealed the presence of an active phytochrome‐binding (APB) domain in the N‐terminal region of six soybean PIF4 homologs. Cis‐elements related to plant hormone biosynthesis, stress response, meristem and endosperm gene expression were located in the promoter region of soybean PIF4s. Interestingly, transgenic soybean plants carrying 35s::GmPIF4b::polyA construct showed reduced plant height, reduced leaf surface area, decreased branching, early flowering and faster transition from full‐bloom flowering stage to full maturity stage without any decline in yield. Further, pod colour of transgenic soybean plants changed to dark brown, whereas wild‐type plants showed tan or light brown pod colour. Clear hilum was observed in seeds obtained from transgenic plants as opposed to the dark or black hilum of wild‐type seeds. Transcripts of soybean florigens GmFT2a and GmFT5a were also elevated in transgenic plants. Collectively, our results suggest that GmPIF4b overexpression could affect phenotypes related to plant morphology and reproductive stages in soybean, and can be used as a gene target for soybean improvement programmes to ensure future food security.

Highlights

Plants’ response to daily and seasonal fluctuations in light and temperature is mediated by perception mechanism which is under the control of complex crosstalks between signalling genes and transcription factors (Foreman et al., 2011; Koini et al, 2009; Kumar et al, 2012; Nomoto et al, 2012; Nozue et al, 2007)
5 ABRE motifs are present in Arabidopsis Phytochrome-interacting factor 4 (PIF4), 7 ABRE motifs are present in GmPIF4a and GmPIF4e promoters, 3 ABRE motifs are present in GmPIF4c, and no ABRE motif is present in GmPIF4b, GmPIF4d, GmPIF4f and GmPIF4g
Multiple sequence alignment of soybean PIF4s with Arabidopsis PIF4 revealed the presence of active phytochrome-b inding (APB) domain in all soybean PIF4s, except GmPIF4e (Figure 1b)

Summary

| INTRODUCTION

Plants’ response to daily and seasonal fluctuations in light and temperature is mediated by perception mechanism which is under the control of complex crosstalks between signalling genes and transcription factors (Foreman et al., 2011; Koini et al, 2009; Kumar et al, 2012; Nomoto et al, 2012; Nozue et al, 2007) Such crosstalks coordinate timing of plant growth and development with the most appropriate time of the day in a favourable season. We reported seven copies of PIF4 (GmPIF4a-g) in soybean, with GmPIF4b identified to be the most likely candidate involved in floral transition based on its expression profile in inductive short days and its ability to induce early flowering in wild-type (WT) Arabidopsis (Arya et al, 2018). We report here that the transgenic soybean lines carrying 35s::GmPIF4b:: polyA construct exhibited changes in plant morphology and showed early onset of flowering with the accelerated transition from early pod formation stage to full maturity stage

| MATERIALS AND METHODS

| RESULTS

Findings

| DISCUSSION