Genome-Wide Identification of ABSCISIC ACID-INSENSITIVE (ABI) Genes and Their Response to MeJA During Early Somatic Embryogenesis in Longan (Dimocarpus longan L.)

Methyl jasmonic acid (MeJA) is a vital phytohormone that plays a key role in plant growth and adaptation to various environmental stresses. In the present study, on the basis of the longan genome, we identified a total of seven versatile putative abscisic acid-insensitive genes, which are the key players in plant growth and stress response. On the basis of bioinformatics analysis, transcriptome data, exogenous treatment experiments, and RT-qPCR findings, a comprehensive evolutionary pattern of ABI genes in different plant species and the effect of different MeJA treatments during early somatic embryogenesis in D. longan was carried out. The phylogeny results revealed that the seven DlABI genes evolved independently in monocots and dicots, having high protein sequence similarity, especially with Arabidopsis ABI genes. The comparative findings of gene structure, motif prediction, and synteny analysis suggest that DlABI genes disperse mainly through duplication events rather than localized tandem repeats. Furthermore, the correlations among the expressions of DlABI genes propose that the organization of the cis-regulatory elements in the promoter regions may regulate the temporal and spatial transcription activation of these genes. The qRT-PCR results revealed that the 50 &micro:M MeJA treatment significantly upregulated the expression of DlABI3, followed by DlABI1, DlABI2, DlABI5, DlABI4, and DlABI8, respectively. The ROS findings clearly revealed that MeJA distinctly elevated the SOD, POD, and H2O2 activities while reducing catalase and MDA contents. The subcellular localization of DlABI3 further confirmed its presence in the nucleus, suggesting its predicated transcriptional regulatory role in MeJA-mediated early SE in longan. Our findings reveal that the ABI genes are integral to the mechanism of MeJA-induced early somatic embryogenesis in longan by maintaining the ROS activity.