Small signaling peptides, generally comprising fewer than 100 amino acids, act as crucial signaling molecules in cell-to-cell communications. Upon perception by their membrane-localized corresponding receptors or co-receptors, these peptide-receptor modules then (de)activate either long-distance or local signaling pathways, thereby orchestrating developmental and adaptive responses via (post)transcriptional, (post)translational, and epigenetic regulations. The physiological functions of small signaling peptides are implicated in a multitude of developmental processes and adaptive responses, including but not limited to, shoot and root morphogenesis, organ abscission, nodulation, Casparian strip formation, pollen development, taproot growth, and various abiotic stress responses such as aluminum, cadmium, drought, cold, and salinity. Additionally, they play a critical role in response to pathogenic invasions. These small signaling peptides also modulate significant agronomic and horticultural traits, such as fruit size, maize kernel development, fiber elongation, and rice awn formation. Here, we underscore the roles of several small signaling peptide families such as CLE, RALF, EPFL, miPEP, CEP, IDA/IDL, and PSK in regulating these biological processes. These novel insights will deepen our current understanding of small signaling peptides, and offer innovative strategies for genetic breeding stress-tolerant crops and horticultural plants, contributing to establish sustainable agricultural systems.

Tonoplast sugar transporters (TSTs) play essential roles in regulating plant growth, development, and response to various biotic and abiotic stresses. In this study, a total of three TST genes were identified by a genome-wide analysis in cucumber. Phylogenetic analysis showed that TST proteins from cucumber and other plant species can be classified into five groups, and nearly all TST members in the same groups displayed similar motif distributions, transmembrane (TM) domains, and gene structures. All of the three CsTST genes possess a number of development-, stress-, and hormone-related cis-elements in the promoter sequences. Meanwhile, qRT-PCR assays revealed that the CsTST1 was expressed in fruits, flowers, leaves, and other tissues, and its expression varied significantly under various abiotic stresses such as cold, salt, drought (PEG), and abscisic acid (ABA). Finally, functional analysis of CsTST1 in yeast revealed that it was able to complement the deficiency in galactose, mannose and sucrose transport. These results revealed that CsTST1 can act as a functional sugar transporter to play important roles in cucumber growth and response to abiotic stress probably through affecting carbohydrate distribution.