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[Display omitted] • A total of 6 GAD family members were systematically identified in the whole genome of longan. DlGAD5 is localized in the cytoplasm. • DlGADs are involved in hormone synthesis and signaling for IAA and ABA in longan SE. • The expression of 6 DlGADs was up-regulated after overexpressing DlGAD5. Moreover, the activity of GAD was enhanced. Glutamate decarboxylase (GAD) is involved in GABA metabolism and plays an essential regulatory role in plant growth, abiotic stresses, and hormone response. This study investigated the expression mechanism of the GAD family during longan early somatic embryogenesis (SE) and identified 6 GAD genes based on the longan genome. Homology analysis indicated that DlGAD genes had a closer relationship with dicotyledonous plants. The analysis of cis -acting elements in the promoter region suggests that the GAD genes were associated with various stress responses and hormones. RNA sequencing (RNA-Seq) and the qRT-PCR data indicated that most DlGAD genes were highly expressed in the incomplete compact pro-embryogenic cultures (ICpEC) and upregulated in longan embryogenic callus (EC) after treatments with 2,4-D, high temperature (35 °C), IAA, and ABA. Moreover, the RNA-Seq analysis also revealed that DlGADs exhibit different expression patterns in various tissues and organs. The subcellular localization results showed that DlGAD5 was localized in the cytoplasm, suggesting that it played a role in the cytoplasm. Transient overexpression of DlGAD5 enhanced the expression levels of DlGADs and increased the activity of glutamate decarboxylase in longan embryogenic callus (EC), while the content of glutamic acid decreased. Thus, the DlGAD gene can play an important role in the early somatic embryogenesis of longan by responding to hormones such as IAA and ABA. DlGAD5 can affect the growth and development of longan by stimulating the expression of the DlGAD gene family, thereby increasing the GAD activity in the early SE of longan, participating in hormone synthesis and signaling pathways. [ABSTRACT FROM AUTHOR]

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 DlRan3A s 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 (GA 3 ), salicylic acid (SA), methyl jasmonate (MeJA), and ethephon (Eth)), salt, sucrose, prolonged culturing period and light quality treatments. IAA (1 mg/L), GA 3 (12 mg/L), SA (75 μm), MeJA (50 and 100 μm), and Eth (50 mg/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, GA 3 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. [ABSTRACT FROM AUTHOR]

• 327 CYP were found from the longan genome, and they exhibited a strong expansion with mainly tandem duplication (TD) events. • DlCYPs expressed higher in globular embryos (GE) compared with those in incomplete compact pro-embryogenic (ICpEC) stage and the embryogenic callus (EC) stage in longan. • DlCYPs had more AS events in ICpEC compared to those in EC and GE. Their transcript isoforms showed expression patterns during early SE in longan. 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 CYP s 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. [ABSTRACT FROM AUTHOR]

Abstract: RAN (Ras-related nuclear protein) plays crucial roles in multiple cellular processes in yeast, animals and plants. Here we present a DlRan gene and its alternative splicing transcripts containing premature terminator codons (PTCs), identified from embryogenic cultures in longan. Multiple alignment and splicing pattern analyses indicated that DlRan-1 transcript harboring PTC was the consequence of alternative splicing. The accumulation of DlRan PTC-containing transcripts increased significantly when the embryogenic calli were treated with the translation inhibitor, cycloheximide, indicating that DlRan-1 may be targeted by NMD. The analysis of expression profiles of DlRan transcripts revealed that differential expression levels of the alternative spliced DlRan transcripts occurred during the development of embryogenic callus, globular-shaped embryos, and cotyledon-shaped embryos, respectively, in the longan somatic embryogenesis, and were in consistent with the embryo development in corresponding wild-type transcripts. The present work offers evidence to speculate that the alternatively spliced PTC-containing transcripts can be functional and may shed light on expression regulation of DlRan during development of the longan somatic embryos. [Copyright &y& Elsevier]