# The age-related expression patterns of Larix kaempferi AP2 subfamily genes and functional dissection of LkTOE1-2 in seed formation and germination

## TL;DR

This study explores genes in Japanese larch that influence seed formation and germination, offering potential for faster tree breeding.

## Contribution

The first genome-wide analysis of AP2/ERF superfamily in conifers and functional characterization of LkTOE1-2.

## Key findings

- 374 AP2/ERF superfamily members were identified in Larix kaempferi.
- LkTOE1-2 over-expression in Arabidopsis accelerates seed germination, bolting, and flowering.
- RUBY reporter system confirmed LkTOE1-2's role in somatic embryo maturation.

## Abstract

Conifers pose challenges for breeding programs due to their extended vegetative phases. Despite the critical role of APETALA2 (AP2) in regulating phase transitions, the AP2/ERF superfamily remains largely unexplored in gymnosperms. Here, the first genome-wide analysis of the AP2/ERF superfamily in a conifer, Larix kaempferi (Japanese larch) is presented, and 374 members were identified. Among all eight paralogs, four euAP2 lineage genes, TARGET OF EATs (TOEs), exhibit age-decreased expression patterns. Functional characterization of LkTOE1-2 demonstrates its involvement in somatic embryogenesis and seed germination. Importantly, the RUBY reporter system confirmed an enhanced promoter activity in somatic embryo maturation. Over-expression of LkTOE1-2 in Arabidopsis accelerates seed germination by 23.77%, bolting by 6.93%, and flowering by 5.92%. This study provides not only an expanded genomic resource for gymnosperms but also a candidate gene (LkTOE1-2) to shorten the juvenile phase of larch via molecular breeding.