Leucine-rich repeat extensin (LRX) is involved in the regulation of crucial cellular processes, such as cell wall growth and development, as well as signaling. However, the presence of the LRX gene family in Brassica rapa (B. rapa) has not been previously reported. This study identified 17 BrLRXs within the Brassica rapa genome by bioinformatic analysis, and these genes were distributed on seven chromosomes. Phylogenetic and covariance analyses indicate that BrLRXs can be categorized into two distinct branches: the trophic branch and the reproductive branch, with a close relationship observed between BrLRXs and AtLRXs. According to cis-acting element analysis, this gene family is rich in hormone-responsive and stress-responsive elements such as drought-inducibility, abscisic acid, methyl jasmonate, and gibberellic acid responsive elements, suggesting a potential role in abiotic stress response. Transcriptomic, proteomic, and RT-qPCR analyses demonstrated significant up-regulation of BrLRX2 and BrLRX6 under salt stress, while BrLRX3, BrLRX6, and BrLRX8 were significantly down-regulated under osmotic stress. Our analysis of the protein tertiary structure predicts a strong association between LRX proteins and RALF. Protein–protein interaction prediction revealed that LRX interacts with the RALF protein and the receptor FER, which have been previously reported to jointly regulate plant stress responses. We propose that BrLRX6 and BrLRX8 are implicated in osmotic stress, while BrLRX2 and BrLRX6 are involved in the modulation of salt stress.

The bile acid sodium symporter (BASS) family plays an important role in transporting substances and coordinating plants’ salt tolerance. However, the function of BASS in Brassica rapa has not yet been elucidated. In this study, eight BrBASS genes distributed on five chromosomes were identified that belonged to four subfamilies. Expression profile analysis showed that BrBASS7 was highly expressed in roots, whereas BrBASS4 was highly expressed in flowers. The promoter element analysis also identified several typical homeopathic elements involved in abiotic stress tolerance and stress-related hormonal responses. Notably, under salt stress, the expression of BrBASS2 was significantly upregulated; under osmotic stress, that of BrBASS4 increased and then decreased; and under cold stress, that of BrBASS7 generally declined. The protein–protein interaction analysis revealed that the BrBASS2 homologous gene AtBASS2 interacted with Nhd1 (N-mediated heading date-1) to alleviate salt stress in plants, while the BrBASS4 homologous gene AtBASS3 interacted with BLOS1 (biogenesis of lysosome-related organelles complex 1 subunit 1) via co-regulation with SNX1 (sorting nexin 1) to mitigate an unfavorable growing environment for roots. Further, Bra-miR396 (Bra-microRNA396) targeting BrBASS4 and BrBASS7 played a role in the plant response to osmotic and cold stress conditions, respectively. This research demonstrates that BrBASS2, BrBASS4, and BrBASS7 harbor great potential for regulating abiotic stresses. The findings will help advance the study of the functions of the BrBASS gene family.

In Brassicaceae cross-breeding, asynchronous flowering and geographic separation often cause pollen shortages that severely constrain hybridization. Although pollen cryopreservation offers an effective solution, Brassicaceae pollen is typically short-lived due to its tricellular structure, thin exine, and high desiccation sensitivity, necessitating optimized cryopreservation protocols. In this study, we optimized a pollen cryopreservation protocol for three representatives Brassicaceae species: Brassica rapa L. (Chinese cabbage), Brassica oleracea L. (cabbage), and Barbarea vulgaris R. Br. (European rockcress). An in vitro pollen germination system was optimized to reliably assess pollen viability before and after cryopreservation. Key parameters including pollen collection time, drying duration, freezing procedure, and thawing conditions were systematically evaluated. The optimal protocol comprised: pollen collection at 8:00–10:00, drying at 28 °C and 2% relative humidity for 1 h, precooling at −20 °C for 30 min, storage at −80 °C, and thawing under running tap water (ca. 25 °C). Following 30-day cryopreservation, pollen maintained high germination rates (75.19% for Brassica rapa L., 71.18% for Brassica oleracea L., 80.33% for Barbarea vulgaris) and produced comparable silique development, seed quality, and seed germination rates to those of fresh pollen following pollination. This study established a reliable and efficient cryopreservation system for Brassicaceae pollen that effectively overcomes asynchronous flowering and geographic barriers in hybridization, thereby improving breeding efficiency and facilitating germplasm innovation for Brassicaceae crops.