The salinization of irrigated land affects agricultural productivity. HIGH‐AFFINITY POTASSIUM (K⁺) TRANSPORTER 1;5 (OsHKT1;5)‐dependent sodium (Na⁺) transport is a key salt tolerance mechanism during rice growth and development. Using a previously generated high‐throughput activation tagging‐based T‐DNA insertion mutant pool, we isolated a mutant exhibiting salt stress‐sensitive phenotype, caused by a reduction in OsHKT1;5 transcripts. The salt stress‐sensitive phenotype of this mutant results from the loss of function of OsDNAJ15, which encodes plasma membrane‐localized heat shock protein 40 (Hsp40). osdnaj15 loss‐of‐function mutants show decreased plant height, increased leaf angle, and reduced grain number caused by shorter panicle length and fewer branches. On the other h'and, OsDNAJ15‐overexpression plants showed salt stress‐tolerant phenotypes. Intriguingly, salt stress facilitates the nuclear relocation of OsDNAJ15 so that it can interact with OsBAG4, and OsDNAJ15 and OsBAG4 synergistically facilitate the DNA‐binding activity of OsMYB106 to positively regulate the expression of OsHKT1;5. Overall, our results reveal a novel function of plasma membrane‐localized Hsp40 protein in modulating, alongside chaperon regulator OsBAG4, transcriptional regulation under salinity stress tolerance.

The Calocybe species possess notable economic and medicinal value, demonstrating substantial potential for resource utilization. The taxonomic studies of Calocybe are lacking in quality and depth. Based on the specimens collected from northeast China, this study provides a detailed description of two newly discovered species, namely Calocybe betulicola and Calocybe cystidiosa, as well as two commonly found species, Calocybe decolorata and Calocybe ionides. Additionally, a previously unrecorded species, C. decolorata, has recently been discovered in Jilin Province, China. The two newly discovered species can be accurately distinguished from other species within the genus Calocybe based on their distinct morphological characteristics. The primary distinguishing features of C. betulicola include its grayish-purple pileus, grayish-brown to dark purple stipe, smaller basidiomata, absence of cellular pileipellis, and its habitat on leaf litter within birch forests. Calocybe cystidiosa is distinguished by its growth on the leaf litter of coniferous forests, a flesh-pink pileus, a fibrous stipe with a white tomentose covering at the base, non-cellular pileipellis, larger basidiospores, and the presence of cheilocystidia. The reconstruction of phylogenetic trees using combined ITS, nLSU, and tef1-α sequences, employing maximum likelihood and Bayesian inference analyses, showed that C. betulicola formed a cluster with C. decurrens, while C. cystidiosa clustered with C. vinacea. However, these two clusters formed separate branches themselves, which also supported the results obtained from our morphological studies. A key to the Calocybe species reported from northeast China is provided to facilitate future studies of the genus.