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.

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.

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