PP2C (protein phosphatases 2C) are key regulators of abscisic acid (ABA) signaling that play a crucial role in plant stress responses. Our analysis identified 71 DlPP2C genes in Dimocarpus longan, which were classified into distinct subgroups based on phylogenetic relationships with Arabidopsis thaliana and Oryza sativa. Structural analysis demonstrated conserved motif composition and gene organization within subgroups, while chromosomal distribution and synteny analysis revealed that segmental duplication events contributed to the expansion of this gene family. Promoter analysis uncovered several cis-acting elements related to hormone and stress responsiveness, especially abscisic acid-responsive elements (ABREs), suggesting that DlPP2C genes may play a role in ABA signaling pathways. Furthermore, we examined the ABA-responsive expression profiles of DlPP2C genes under exogenous ABA treatments. The expression patterns were dynamic and dose- and time-dependent, with several genes showing peak expression at 10 μM ABA after 16 h. The DlPP2C1 in particular displayed a strong transcriptional response, indicating its potential role in ABA regulation. While overexpression and GUS staining assays revealed enhanced activity under ABA treatment, further supporting the involvement of PP2C in ABA-responsive regulation, further mechanistic studies are needed for a full characterization. Finally, RNA sequencing analysis revealed a total of 1799 differentially expressed genes in response to ABA, with a prevalence of downregulated genes, showing extensive transcriptional reprogramming. Functional enrichment analysis demonstrated that these genes were largely associated with plant hormone signaling, stress response, and metabolic pathways. Weighted gene co-expression network analysis revealed a total of 32 key gene modules associated with ABA signaling. Collectively, our findings propose that DlPP2C genes, especially DlPP2C1, play a key role in ABA-mediated regulatory networks and provide valuable insights into stress adaptation mechanisms, especially during early somatic embryogenesis in longan.

Banana productivity is severely limited by drought, yet the molecular basis of drought adaptation and endophyte-mediated stress alleviation remains poorly understood. Here, we performed a genome-wide analysis of the SQUAMOSA promoter-binding protein-like (SPL) transcription factor family in Musa acuminata and examined their transcriptional responses to drought stress and Serendipita indica inoculation. We identified 38 MaSPL genes, all encoding proteins with the conserved SBP domain and predicted nuclear localization. Phylogenetic, motif, gene structure, and collinearity analyses indicated that MaSPL genes are evolutionarily conserved, unevenly distributed across chromosomes, and expanded primarily through segmental duplication under purifying selection. Promoter analysis showed several cis-acting elements and transcription factor binding sites related to light, phytohormone, and stress signaling. Ten MaSPL genes were predicted as putative targets of miR156. qRT-PCR analysis showed that drought stress markedly downregulated the tested MaSPL genes, whereas miR156a expression increased, supporting an inverse regulatory relationship. Under drought, S. indica inoculation enhanced expression of most tested MaSPLs, restoring transcript accumulation while reducing miR156a to near-basal levels. Notable responses were observed in members of the MaSPL2, MaSPL9, and MaSPL13, respectively. S. indica improves drought tolerance by enhancing antioxidant defenses, reducing oxidative stress, and preserving photosynthetic and osmotic stability. Taken together, our results demonstrate that S. indica confers drought resilience in banana by counteracting drought-induced repression of MaSPL genes via the miR156–SPL module and by strengthening key physiological defense mechanisms.

The PP2C (protein phosphates 2C) are key regulators of abscisic acid (ABA) signaling that play a crucial role in plant stress responses. In this study, we performed a comprehensive genome-wide analysis and identified 71 DlPP2C genes in Dimocarpus longan which is an economically important fruit crop. The evolutionary analysis revealed that DlPP2C genes were classified into distinct subgroups based on phylogenetic relationships with Arabidopsis thaliana and Oryza sativa. Structural analysis demonstrated conserved motif composition and gene organization within subgroups, whereas chromosomal distribution and synteny analysis revealed that segmental duplication events contributed to gene family expansion. Promoter analysis findings identified numerous cis-acting elements related to hormone and stress responsiveness especially abscisic acid-responsive elements (ABREs), suggesting their potential involvement in ABA signaling pathways. Under exogenous ABA treatments, expression profiling of the DlPP2C genes exhibited dynamic, dose and time dependent response with several genes showing peak expression at 10 μM ABA after 16 h, especially the DlPP2C1 displayed a strong transcriptional response, indicating its potential role as a key regulator. Overexpression and GUS staining assays revealed enhanced activity under ABA treatment, further supporting its involvement in ABA-responsive regulation. Moreover, RNA sequencing analysis revealed a total of 1799 differentially expressed genes, with prevalence of downregulated genes, showing extensive transcriptional reprograming. Functional enrichment analysis demonstrated that these genes were largely associated with plant hormone signaling, stress response and metabolic pathways. Together, these findings propose that DlPP2C genes, especially DlPP2C1, play a key role in ABA-mediated regulatory networks and provide valuable insights intro stress adaption mechanisms during early somatic embryogenesis in longan.