Non-coding RNAs (ncRNAs) that were once considered “dark matter” or “transcriptional noise” in genomes are research hotspots in the field of epigenetics. The most well-known microRNAs (miRNAs) are a class of short non-coding, small molecular weight RNAs with lengths of 20–24 nucleotides that are highly conserved throughout evolution. Through complementary pairing with the bases of target sites, target gene transcripts are cleaved and degraded, or translation is inhibited, thus regulating the growth and development of organisms. Unlike miRNAs, which have been studied thoroughly, long non-coding RNAs (lncRNAs) are a group of poorly conserved RNA molecules with a sequence length of more than 200 nucleotides and no protein encoding capability; they interact with large molecules, such as DNA, RNA, and proteins, and regulate protein modification, chromatin remodeling, protein functional activity, and RNA metabolism in vivo through cis- or trans-activation at the transcriptional, post-transcriptional, and epigenetic levels. Research on plant lncRNAs is just beginning and has gradually emerged in the field of plant molecular biology. Currently, some studies have revealed that lncRNAs are extensively involved in plant growth and development and stress response processes by mediating the transmission and expression of genetic information. This paper systematically introduces lncRNA and its regulatory mechanisms, reviews the current status and progress of lncRNA research in plants, summarizes the main techniques and strategies of lncRNA research in recent years, and discusses existing problems and prospects, in order to provide ideas for further exploration and verification of the specific evolution of plant lncRNAs and their biological functions.

Soil salinization is an increasingly serious threat that limits plant growth and development. Class I transporters of the high-affinity K⁺ transporter (HKT) family have been demonstrated to be involved in salt tolerance by contributing to Na⁺ exclusion from roots and shoots. Here, we isolated the PeHKT1;1 gene from hybrid poplar based on the sequences of the Populus trichocarpa genome. The full-length PeHKT1;1 gene was 2173 bp, including a 1608 bp open reading frame (ORF) encoding 535 amino acids and containing eight distinct transmembrane domains. Multiple sequence alignment and phylogenetic analysis suggested that the PeHKT1;1 protein had a typical S–G–G–G signature for the P-loop domains and belonged to class I of HKT transporters. PeHKT1;1 transcripts were mainly detected in stem and root, and were remarkably induced by salt stress treatment. In further characterization of its functions, overexpression of PeHKT1;1 in Populus davidiana × Populus bolleana resulted in a better relative growth rate in phenotypic analysis, including root and plant height, and exhibited higher catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities than non-transgenic poplar under salt stress conditions. These observations indicated that PeHKT1;1 may enhance salt tolerance by improving the efficiency of antioxidant systems. Together, these data suggest that PeHKT1;1 plays an important role in response to salt stress in Populus.