Fox Hunting in Wild Apples: Searching for Novel Genes in Malus Sieversii.

Michael Wisniewski,Timothy Artlip,John Norelli,Erik Burchard,Jia Liu,Jing Ma,Christopher Dardick

doi:10.3390/ijms21249516

Abstract

Malus sieversii is considered the progenitor of modern apple (Malus pumila) cultivars and to represent a valuable source of genetic diversity. Despite the importance of M. sieversii as a source of disease resistance, stress tolerance, and novel fruit traits, little is known about gene function and diversity in M. sieversii. Notably, a publicly annotated genome sequence for this species is not available. In the current study, the FOX (Full-length cDNA OvereXpressing) gene hunting system was used to construct a library of transgenic lines of Arabidopsis in which each transgenic line overexpresses a full-length gene obtained from a cDNA library of the PI619283 accession of M. sieversii. The cDNA library was constructed from mRNA obtained from bark tissues collected in late fall–early winter, a time at which many abiotic stress-adaptative genes are expressed. Over 4000 apple FOX Arabidopsis lines have been established from the pool of transgenic seeds and cDNA inserts corresponding to various Gene Ontology (GO) categories have been identified. A total of 160 inserts appear to be novel, with no or limited homology to M. pumila, Arabidopsis, or poplar. Over 1300 lines have also been screened for freezing resistance. The constructed library of transgenic lines provides a valuable genetic resource for exploring gene function and diversity in Malus sieversii. Notably, no such library of t-DNA lines currently exists for any Malus species.

Highlights

The domesticated apple (Malus pumila) is an important agricultural commodity with an average annual production of 4.57 million metric tons in the United States, with a value approaching four billion US dollars [1]
Over 4000 independent T2 lines have been entered into a local database, with 2888 inserts annotated by BLASTN comparison to the “Golden Delicious” Doubled Haploid (GDDH) genome (GDR) and the Non-Redundant National Center for Biotechnology Information (NCBI) mRNA database (Supplementary Materials Tables S1 and S2)
A novel resource for the analysis of gene function and diversity in M. sieversii, a wild apple species recognized as a progenitor of the domestic apple (M. pumila), was created using the Full-length cDNA OvereXpressing (FOX) hunting system [25]

Summary

Introduction

The domesticated apple (Malus pumila) is an important agricultural commodity with an average annual production of 4.57 million metric tons in the United States, with a value approaching four billion US dollars [1]. Over 75 million metric tons were produced in 2018/2019 [2]. Data from the USDA Risk Management Agency for the years 2007–2017 indicates that apple growers claimed $157,177,390 in insured losses from freeze damage [7]. These impacts will continue and may increase due the global transport of new diseases or pathogenic strains, invasive pests and increased levels of environmental stress (temperature, water) brought on by climate change

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