The APETALA2 homolog CaFFN regulates flowering time in pepper

Xinjie Yuan,Rong Fang,Xuejun Chen,Kunhua Zhou,Xiaowu Wang,Gang Lei,Yueqin Huang

doi:10.1038/s41438-021-00643-7

Abstract

Flowering time is an important agronomic trait that contributes to fitness in plants. However, the genetic basis of flowering time has not been extensively studied in pepper. To understand the genetics underlying flowering time, we constructed an F2 population by crossing a spontaneous early flowering mutant and a late-flowering pepper line. Using bulked segregant RNA-seq, a major locus controlling flowering time in this population was mapped to the end of chromosome 2. An APETALA2 (AP2) homolog (CaFFN) cosegregated with flowering time in 297 individuals of the F2 population. A comparison between the parents revealed a naturally occurring rare SNP (SNP2T > C) that resulted in the loss of a start codon in CaFFN in the early flowering mutant. Transgenic Nicotiana benthamiana plants with high CaFFN expression exhibited a delay in flowering time and floral patterning defects. On the other hand, pepper plants with CaFFN silencing flowered early. Therefore, the CaFFN gene acts as a flowering repressor in pepper. CaFFN may function as a transcriptional activator to activate the expression of CaAGL15 and miR156e and as a transcriptional repressor to repress the expression of CaAG, CaAP1, CaSEP3, CaSOC1, and miR172b based on a qRT-PCR assay. Direct activation of CaAGL15 by CaFFN was detected using yeast one-hybrid and dual-luciferase reporter assays, consistent with the hypothesis that CaFFN regulates flowering time. Moreover, the CaFFN gene association analysis revealed a significant association with flowering time in a natural pepper population, indicating that the CaFFN gene has a broad effect on flowering time in pepper. Finally, the phylogeny, evolutionary expansion and expression patterns of CaFFN/AP2 homologs were analyzed to provide valuable insight into CaFFN. This study increases our understanding of the involvement of CaFFN in controlling flowering time in pepper, thus making CaFFN a target gene for breeding early maturing pepper.

Highlights

The timing of the transition from vegetative growth to flowering is a major factor that ensures that plants produce enough progeny for their sustainable development[1,2,3]
Genetic analysis of the flowering time trait in pepper A natural precocious variant was discovered in our breeding work, from which a stable early flowering inbred line named B9431 was created after years of selfing and selective breeding (Fig. 1a)
The results showed that CaFFN directly interacted with CaAGL15, since yeast transformed with pGADT7-CaFFN and the bait vector grew in SD/-Leu selection medium supplemented with the minimal inhibitory concentration of aureobasidin A (AbA), while yeast transformed with pGADT7-lam and pAbAi-P53, as a negative control, did not (Fig. 4c)

Summary

Introduction

The timing of the transition from vegetative growth to flowering is a major factor that ensures that plants produce enough progeny for their sustainable development[1,2,3]. AP2 positively regulates miR156 and negatively regulates miR172 to form a complex direct feedback loop that influences AP2 expression[10]. Solanaceae includes species such as potato (Solanum tuberosum), tomato (S. lycopersicum), pepper (Capsicum annuum), eggplant (S. melongena), and tobacco (Nicotiana tabacum) that are of agricultural interest or research interest. Among these species, tomato has been more extensively studied for the control of flowering time[11,12,13]

Methods

Results

Conclusion