Frame-shift mutation ofInCOmight cause early flowering of Japanese morning glory and might have contributed to northward expansion

Abstract

AbstractJapanese morning glory (Ipomoea nil), a short day plant, has been used for studying flowering times. Here, quantitative trait loci (QTL) analysis for days from sowing to flowering (DTF) of F2betweenI. nilvar. Tokyo Kokei Standard (TKS) andI. hederacealine var. Q65, an early flowering variety, revealed four QTLs:QTL Ipomoea Flowering 1–4(qIF1–4). The position ofqIF3, which had the most significant effect among the four QTLs, corresponds with that ofI. nil(orI. hederacea)CONSTANS(InCO/IhCO) in the linkage map. There is a single-base In/Del in the coding sequence ofInCO/IhCO. The single-base deletion (SBD) causes a frame-shift mutation and loss of function in TKS allele (inco-1).I. nilaccessions bearinginco-1tend to flower early, similarly to rice varieties bearing the loss of function allele ofCOortholog,hd1. Consequently,inco-1was inferred to reduce DTF. This inferred effect ofinco-1corresponds with the effect of the TKS allele ofqIF3. Becauseinco-1is found exclusively in Asian accessions, the SBD ininco-1might have played an important role in the expansion of Japanese morning glories, originally native to the tropical regions of the Americas, into temperate Asia.