Stress Regulatory capabilities discovered in late embryogenesis abundant (LEA) proteins expressed during pecan (Carya...

Pecan (Carya illinoinensis), a major North American tree nut crop, faces yield losses due to abiotic stressors like drought and salinity. Late embryogenesis abundant (LEA) proteins, known for stabilizing cellular components under desiccation, remain uncharacterized in pecans. This study bridges this gap by analysing LEA proteins during kernel development in 'Sumner' and 'Pawnee' cultivars, combining phylogenetic, structural, and functional analyses to elucidate their roles in stress adaptation.

We identified 43 LEA proteins across seven subfamilies, with LEA2 as the largest subgroup (30 members). Phylogenetic analysis revealed strong conservation with Arabidopsis homologs. Structural characterization highlighted hydrophilic properties in LEA4 and dehydrins, critical for stress mitigation. Transcriptomic profiling revealed cultivar-specific expression patterns, with 'Sumner' nuts displaying high CiPLEA1.1 and CiPLEA4.1 gene expression, while 'Pawnee' upregulated CiPLEA4.1 and CiPLEA3.1. Heterologous expression in Escherichia coli demonstrated that LEAP3 and LEAP4 conferred enhanced tolerance to osmotic stress (0.4 M NaCl/sorbitol) and desiccation, with LEAP4 expressing cells showing a 2.5-fold growth advantage under salinity. In micropropagated pecan plants, LEAP4 expression surged transiently under 75 mM NaCl, peaking at 48 h, indicating LEAP4 functions as an early stress responder.

This is the first comprehensive study of pecan LEA proteins and underscores LEAP4's dual role in osmotic adjustment and desiccation tolerance, positioning it as a key candidate for improving abiotic stress resilience. The molecular insights on stress adaptation mechanisms gained through the conserved yet diverse LEA family in pecan kernels enables us to explore LEA-mediated regulatory networks across diverse abiotic stress conditions to mitigate crop losses in perennial tree crops, with implications for breeding programs and postharvest storage protocols.