Long non-coding RNAs as Emerging Regulators of Agronomic Traits: Molecular Mechanisms, Functional Landscape and Prospects for Crop Improvement

Long non-coding RNAs (lncRNAs) are transcripts longer than 200 nucleotides with little or no protein-coding capacity. Once dismissed as transcriptional noise, they are now recognised as versatile regulators of gene expression that act through chromatin remodelling, transcriptional interference, microRNA target mimicry, modulation of alternative splicing and the formation of RNA–DNA hybrids. In plants, lncRNAs have been linked to many traits of agronomic value, including flowering time and vernalisation response, photoperiod-sensitive male sterility used in two-line hybrid rice, grain yield, fruit ripening, and tolerance to drought, salinity, cold, heat and pathogens. Genome-wide surveys in rice, maize, wheat, tomato and Arabidopsis have catalogued thousands of lncRNAs, and dedicated databases now support their annotation. This review summarises the classification and modes of action of plant lncRNAs, discusses well-characterised examples that bear directly on crop performance, and examines how lncRNAs can be exploited as molecular markers, engineering targets and regulatory tools in breeding programmes. Current limitations, including low sequence conservation, poor functional annotation and the difficulty of editing non-coding loci, are discussed together with future directions for translating lncRNA biology into improved crop varieties.