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Calcineurin B-like protein-interacting protein kinases (CIPKs) play important roles in plant responses to stress. However, their function in the ornamental woody plant Lagerstroemia indica is remains unclear. In this study, the LiCIPK gene family was analyzed at the whole genome level. A total of 37 LiCIPKs, distributed across 17 chromosomes, were identified. Conserved motif analysis indicated that all LiCIPKs possess a protein kinase motif (S_TKc) and C-terminal regulatory motif (NAF), while seven LiCIPKs lack a protein phosphatase interaction (PPI) motif. 3D structure analysis further revealed that the N-terminal and C-terminal 3D-structure of 27 members are situated near to each other, while 4 members have a looser structure, and 6 members lack intact structures. The intra- and interspecies collinearity analysis, synonymous substitution rate (Ks) peaks of duplicated LiCIPKs, revealed that ∼80% of LiCIPKs were retained by the two whole genome duplication (WGD) events that occurred approximately 56.12–61.16 million year ago (MYA) and 16.24–26.34 MYA ago. The promoter of each LiCIPK contains a number of auxin, abscisic acid, gibberellic acid, salicylic acid, and drought, anaerobic, defense, stress, and wound responsive cis-elements. Of the 21 members that were successfully amplified by qPCR, 18 LiCIPKs exhibited different expression patterns under NaCl, mannitol, PEG8000, and ABA treatments. Given that LiCIPK30, the AtSOS2 ortholog, responded to all four types of stress it was selected for functional verification. LiCIPK30 complements the atsos2 phenotype in vivo. 35S:LiCIPK-overexpressing lines exhibit increased leaf area increment, chlorophyll a and b content, reactive oxygen species scavenging enzyme activity, and expression of ABF3 and RD22, while the degree of membrane lipid oxidation decreases under NaCl treatment compared to WT. The evolutionary history, and potential mechanism by which LiCIPK30 may regulate plant tolerance to salt stress were also discussed. In summary, we identified LiCIPK members involved in abiotic stress and found that LiCIPK30 transgenic Arabidopsis exhibits more salt and osmotic stress tolerance than WT. This research provides a theoretical foundation for further investigation into the function of LiCIPKs, and for mining gene resources to facilitate the cultivation and breeding of new L. indica varieties in coastal saline-alkali soil.

The hyperosmolality-gated calcium-permeable channels (OSCA) play an imperative role in the plant response to environmental stresses. Moreover, their characteristics in the ornamental woody plant Liriodendron chinense, widely dispersed in the southern region of China, is yet to be elucidated. In the present study, 399 OSCA proteins were identified from 31 plant genomes, and comparative phylogenetic analysis revealed that LchiOSCAs gene family is closely related to the Magnolia Cinnamomum kanehirae OSCAs. In L. chinense, 11 LchiOSCA genes were identified and distributed across eight chromosomes. Additionally, phylogenetic analysis of LchiOSCAs exhibited a classification into four subfamilies based on the tree arrangement, similarity in the gene structures, and conserved motif numbers and order. Gene duplication investigations were biased towards the tandem duplication events, accounting for 36% (4/11) of the LchiOSCA gene family. The interspecies collinearity analysis revealed a closer relationship between the L. chinense OSCAs and the P. trichocarpa OSCAs. Analysis in promoter regions of the LchiOSCAs showed the presence of multiple phytohormones and stress responsive elements. Specifically, the ABA-responsive elements had the greatest representation. 3D protein structures of the modeled L. chinense OSCAs exhibited a high homology with the template structures, providing a better understanding of LchiOSCAs’ functionality at the proteome level. The expression pattern analysis of LchiOSCAs based on the transcriptome data and qRT-PCR in L. chinense leaves showed differential responses to drought, cold, and heat stress at varying degrees. Specifically, LchiOSCA2 and LchiOSCA4 were highly expressed under the three abiotic stresses. This research will provide valuable resources and further the understanding of plant OSCA genes in L. chinense for agronomic breeding and bio-engineering purposes.

Heat shock proteins (HSPs) are conserved molecular chaperones whose main role is to facilitate the regulation of plant growth and stress responses. The HSP gene family has been characterized in most plants and elucidated as generally stress-induced, essential for their cytoprotective roles in cells. However, the HSP gene family has not yet been analyzed in the Liriodendron chinense genome. In current study, 60 HSP genes were identified in the L. chinense genome, including 7 LchiHSP90s, 23 LchiHSP70s, and 30 LchiHSP20s. We investigated the phylogenetic relationships, gene structure and arrangement, gene duplication events, cis-acting elements, 3D-protein structures, protein–protein interaction networks, and temperature stress responses in the identified L. chinense HSP genes. The results of the comparative phylogenetic analysis of HSP families in 32 plant species showed that LchiHSPs are closely related to the Cinnamomum kanehirae HSP gene family. Duplication events analysis showed seven segmental and six tandem duplication events that occurred in the LchiHSP gene family, which we speculated to have played an important role in the LchiHSP gene expansion and evolution. Furthermore, the Ka/Ks analysis indicated that these genes underwent a purifying selection. Analysis in the promoter region evidenced that the promoter region LchiHSPs carry many stress-responsive and hormone-related cis-elements. Investigations in the gene expression patterns of the LchiHSPs using transcriptome data and the qRT-PCR technique indicated that most LchiHSPs were responsive to cold and heat stress. In total, our results provide new insights into understanding the LchiHSP gene family function and their regulatory mechanisms in response to abiotic stresses.