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LysM (Lysin motif), in response to pathogenic molecular stresses, is a crucial signal recognition gene. To understand the molecular characteristics of banana LysM gene family members, we used a series of bioinformatics methods. Based on the genomic databases of Musa acuminata, Musa balbisiana and Musa itinerans, a total of 53 genes and 55 proteins were identified, with 21 genes and 23 proteins in the M.acuminata, 16 genes and 16 proteins in each of M.balbisiana and M.itinerans, respectively. According to the conserved structural domains, LysM can be divided into five classes, namely LysMMltD, LYK, LYP, LysMn, and LysMe. The LysM gene was relatively highly conserved in the evolution of the three genomes of banana, and some differences occurred. Expression analysis revealed that MaLysM4-5 was relatively highly expressed under high-temperature stress, low-temperature stress and pathogen infection; at the same time, about one-third of the members were down-regulated under low-temperature stress and high-temperature stress, while the expression of MaLysM10-1 and MaLysM4-5 were up-regulated. After the banana wilt fungus FocTR4 infected the banana roots, MaLysM1 was down-regulated and MaLysM11-1 was up-regulated. In conclusion, our study suggests that MaLysMs may be necessary in the response to high- and low-temperature stresses, as well as the banana wilt fungus infestation. Overall, this paper found that LysM genes may be involved in biotic and abiotic stresses in banana, and provided helpful information about LysM's evolution, expression and properties, which will provide theoretical references for further studies on the functions of LysM genes and resistance breeding in the future.

Cytochrome P450 (CYP), a multi-gene superfamily, is involved in a broad range of physiological processes, including hormone responses and secondary metabolism throughout the plant life cycle. Longan (Dimocarpus longan), a subtropical and tropical evergreen fruit tree, its embryonic development is closely related to the yield and quality of fruits. And a large number of secondary metabolites, such as flavonoids and carotenoids, are also produced during the longan somatic embryogenesis (SE). It is important, therefore, to study potential functions of CYPs in longan. However, the knowledge of longan CYPs is still very limited. Here, a total of 327 DlCYPs were identified using the genome-search method, which could be classified into nine clans. The expansion of the DlCYP family was mainly caused by tandem duplication (TD) events. Promoter cis-acting elements analysis elucidated that DlCYPs played important roles in hormonal responses. A total of 246 DlCYPs exhibited six different expression patterns during the early SE based on longan transcriptomic data. Eight DlCYPs underwent alternative splicing (AS) events, and they might produce one to six isoforms. And the AS transcript of DlCYP97C1 might act as an alternative to the full-length transcript in ICpEC and GE stages. Finally, protein-protein interaction (PPI) networks and miRNA target prediction elucidated that DlCYPs might be involved in the phenylpropanoid metabolic pathway and primarily regulated and targeted by miR413. In summary, our results provided valuable inventory for understanding the classification and biological functions of DlCYPs and provided insight into further functional verification of DlCYPs during the longan early SE.

Core cell cycle genes (CCCs) are essential regulators of cell cycle operation. In this study, a total of 69 CCCs family members, including 37 CYCs, 20 CDKs, five E2F/DPs, three KRPs, two RBs, one CKS and one Wee1, were identified from the longan genome. Phylogenetic and motifs analysis showed the evolutionary conservation of CCCs. Transcriptome dataset showed that CCCs had various expression patterns during longan early somatic embryogenesis (SE). Either CKS or CYCD3;2 silencing increased the expression of RB-E2F pathway genes, and the silencing of CYCD3;2 might induce the process of apoptosis in longan embryogenic callus (EC) cells. In addition, The qRT-PCR results showed that the expression levels of CDKG2, CYCD3;2, CYCT1;2, CKS and KRP1 were elevated by ABA, 2,4-D and PEG4000 treatments, while CDKG2 and CYCT1;2 were inhibited by NaCl treatment. In conclusion, our study provided valuable information for understanding the characterization and biological functions of longan CCCs.

ADP-ribosylation modification considered as a model to study histone post-translational modification in chromatin modification. Despite it was reported in many plants, the study of ARFs gene family in longan was still unclear. In this study, 14 longan ARFs genes were identified using the longan genome (the third-generation genome) and further divided into two major groups, including the DlARF in the I-II group and the ARF-like (DlARL) in the III-V group, according to their structure and evolutionary characteristics. Whole-genome duplication (WGD) and segmental duplication events played a major role in the expansion of the DlARFs gene family, the synteny and phylogenetic analyses provided a deeper insight into the evolutionary characteristics of the DlARFs. Protein-protein interactions suggested that some DlARFs proteins may interact to participate in biological processes. Promoter analysis showed more stress response elements in DlARF5, DlGB1, DlARL1, DlARL2, and DlARL8a, suggesting that they may participate in abiotic stress. Expression profiles of DlARFs by quantitative real-time PCR (qRT-PCR) showed that they were abundant accumulation during early somatic embryogenesis (SE). Expression pattern analysis of RNA-seq and qRT-PCR revealed that some ARFs members regulated early SE, and respond to exogenous hormones and abiotic stress such as abscisic acid (ABA), gibberellin A3 (GA3), salicylic acid (SA), methyl jasmonate (MeJA), cold, and heat. Our study provides new insights for further research on the potential function of DlARFs, which may be useful for the improvement of longan.

Ras-related nuclear protein (Ran) GTPase plays an important role in nucleo-cytoplasmic transportation of proteins and RNA, mitotic spindle assembly, microtubule assembly and nuclear envelope (NE) assembly. We previously identified the full-length cDNAs and a DNA of DlRan3A from longan (Dimocarpus longan Lour.) somatic embryos and demonstrated its possible roles in cell activities during longan somatic embryogenesis (SE). However, thus far little is known of how Ran functions in the signaling pathways in plant embryos in response to changing environmental stimuli. To discover more biological roles of DlRan3A, we observed DlRan3A located in the nucleus and detected abundant accumulation of DlRan3As in globular and cotyledon embryos during longan SE, which suggested its involvement in auxin signal pathways in longan early SE. The transcript level of the DlRan3A gene were also determined in longan embryogenic callus (EC) in response to different levels of exogenous phytohormones (indoleacetic acid (IAA), gibberellin A3 (GA3), salicylic acid (SA), methyl jasmonate (MeJA), and ethephon (Eth)), salt, sucrose, prolonged culturing period and light quality treatments. IAA (1mg/L), GA3 (12 mg/L), SA (75 μm), MeJA (50 and 100 μm), and Eth (50mg/L) modulate expression of DlRan3A to 1.3-1.4 folds, and the expression of DlRan3A was significantly affected by light quality, significantly induced to 2-fold by salt (10 g/L), 2.7-fold by sucrose (90 g/L) and was completely suppressed by prolonged cultivation (>40 days). Deletion analysis suggested that both activation and repression regulatory elements co-exist in the DlRan3A promoter sequence and that the key cis-acting elements included ones in response to auxin, SA, MeJA, and stress. Promoter activities were induced to the highest level by IAA followed by SA, GA3 and MeJA, while suppressed by ABA and Eth. Together, these results showed DlRan3A close involvement in phytohormones, light, and abiotic stress responsiveness during longan SE.