Genome-Wide Identification of NLP Family Genes in Cultivated Strawberry (Fragaria × ananassa Duch.) and Analysis of Their Expression Under Heat and Botrytis cinerea Stresses

Abstract

Nodule inception (NIN)-like proteins (NLPs) are plant-specific transcription factors regulating nutrient absorption, growth, and stress tolerance; however, their roles in stress responses remain largely uncharacterized. Cultivated strawberry (Fragaria × ananassa ‘Camarosa’) serves as an ideal model for dissecting the evolution and function of NLP genes. In this study, 37 FaNLP genes were identified genome-wide. Phylogenetic analysis classified them into three subfamilies, which are evenly distributed across seven chromosomes. Divergent exon–intron structures and conserved motif compositions suggest functional differentiation among FaNLPs. Quantitative real-time PCR (qRT-PCR) revealed distinct expression profiles under heat stress and Botrytis cinerea infection. Notably, FaNLPs were significantly more upregulated in the cultivar ‘Shuxing’ than in ‘Benihoppe’. Heat stress inhibited photosynthesis and altered catalase activity (CAT), superoxide dismutase activities (SOD) and peroxidase activities (POD), whereas fungal infection enhanced chitinase activity in both cultivars. Comparative genomics with Arabidopsis and rice revealed strawberry-specific evolutionary patterns of NLPs. Subcellular localization prediction indicates that FaNLP proteins primarily localize to the nucleus, implying their potential roles as transcriptional regulators. This study links FaNLP sequence characteristics with stress response phenotypes, providing a foundation for elucidating NLP-mediated regulatory networks in strawberry. Future functional assays, including overexpression and knockout analyses, will further clarify the biological roles of FaNLPs.