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Background: Annexin (ANN) is calcium (Ca 2+ )-dependent and phospholipid binding protein family, which is involved in plant growth and development and response to various stresses. However, little known about ANN genes were identified from crape myrtle, an ornamental horticultural plant widely cultivated in the world., Results: Here, 9 LiANN genes were identified from Lagerstroemia indica, and their characterizations and functions were investigated in L. indica for the first time. The LiANN genes were divided into 2 subfamilies. The gene structure, chromosomal location, and collinearity relationship were also explored. In addition, the GO annotation analysis of these LiANNs indicated that they are enriched in molecular functions, cellular components, and biological processes. Moreover, transcription factors (TFs) prediction analysis revealed that bHLH, MYB, NAC, and other TFs can interact with the LiANN promoters. Interestingly, the LiANN2/4/6-9 were demonstrated to play critical roles in the branching architecture of crape myrtle. Furthermore, the LiANN2/6/8/9 were differentially expressed under salt treatment, and a series of TFs regulating LiANN2/6/8/9 expression were predicted to play essential roles in salt resistance., Conclusions: These results shed light on profile and function of the LiANN gene family, and lay a foundation for further studies of the LiANN genes., (© 2024. The Author(s).)

In the realm of ornamental horticulture, crape myrtle (Lagerstroemia indica) stands out for its aesthetic appeal, attributed largely to its vibrant flowers and distinctive branching architecture. This study embarked on a comprehensive exploration of the gibberellin oxidase (GAox) gene family in crape myrtle, illuminating its pivotal role in regulating GA levels, a key determinant of plant developmental processes. We identified and characterized 36 LiGAox genes, subdivided into GA2ox, GA3ox, GA20ox, and GAox-like subgroups, through genomic analyses. These genes' evolutionary trajectories were delineated, revealing significant gene expansions attributed to segmental duplication events. Functional analyses highlighted the divergent expression patterns of LiGAox genes across different crape myrtle varieties, associating them with variations in flower color and branching architecture. Enzymatic activity assays on selected LiGA2ox enzymes exhibited pronounced GA2 oxidase activity, suggesting a potential regulatory role in GA biosynthesis. Our findings offered a novel insight into the molecular underpinnings of GA-mediated growth and development in L. indica , providing a foundational framework for future genetic enhancements aimed at optimizing ornamental traits. • A total 36 LiGAox genes were identified from the Lagerstroemia indica. • The LiGAoxs participated in formation of flower colours and branching architecture. • The LiGA2ox2 displayed higher GA2 oxidase vitality, implying LiGA2ox2 participates in GA metabolism. [ABSTRACT FROM AUTHOR]

• The endodermal cells and phloem fibers play an essential role in the horizontal branch architecture. • Large numbers of differentially expressed genes (DEGs) are identified between normal condition and Gravitropic growth. • The GA biosynthesis and signal transduction, starch and sucrose metabolism, and plant MAPK signaling pathway are identify to be close associations with the branching architecture in response to gravity signal. The branching architecture, as the main category of plant architecture, has a profound impact on creating natural beauty and plant production. Also, the gravitropic responses are involved in directional growth of all plants on earth. The crape myrtle as a kind of important ornamental plants is widely applied to urban landscaping. However, the regulatory mechanism controlling the branching architecture in response of gravity signal is poorly understood in crape myrtle. To identify the putative molecular mechanism, the transcriptome sequencing of crape myrtle in gravitropic growth was performed. Paraffin section analysis displayed dominant difference in the horizontal and erect branches. Also, large numbers of differentially expressed genes (DEGs) were identified between normal condition and gravitropic growth. Based on the KEGG analysis, the DEGs were mainly enriched in GA biosynthesis and signal transduction, starch and sucrose metabolism, and plant MAPK signaling pathway. This research enhanced our molecular comprehension of branching architecture in response to gravity signal while also enabling the practical application of these insights to improved crape myrtle as a significant ornamental species. [ABSTRACT FROM AUTHOR]