Background: Eucalyptus is a highly diverse genus of the Myrtaceae family and widely planted in the world for timber and pulp production. Tissue culture induced callus has become a common tool for Eucalyptus breeding, however, our knowledge about the genes related to the callus maturation and shoot regeneration is still poor. Results: We set up an experiment to monitor the callus induction and callus development of two Eucalyptus species - E. camaldulensis (high embryogenic potential) and E. grandis x urophylla (low embryogenic potential). Then, we performed transcriptome sequencing for primary callus, mature callus, shoot regeneration stage callus and senescence callus. We identified 707 upregulated and 694 downregulated genes during the maturation process of the two Eucalyptus species and most of them were involved in the signaling pathways like plant hormone and MAPK. Next, we identified 135 and 142 genes that might play important roles during the callus development of E. camaldulensis and E. grandis x urophylla, respectively. Further, we found 15 DEGs shared by these two Eucalyptus species during the callus development, including Eucgr.D00640 (stem-specific protein TSJT1), Eucgr.B00171 (BTB/POZ and TAZ domain-containing protein 1), Eucgr.C00948 (zinc finger CCCH domain-containing protein 20), Eucgr.K01667 (stomatal closure-related actinbinding protein 3), Eucgr.C00663 (glutaredoxin-C10) and Eucgr.C00419 (UPF0481 protein At3g47200). Interestingly, the expression patterns of these genes displayed “N” shape in the samples. Further, we found 51 genes that were dysregulated during the callus development of E. camaldulensis but without changes in E. grandis x urophylla, such as Eucgr.B02127 (GRF1-interacting factor 1), Eucgr.C00947 (transcription factor MYB36), Eucgr.B02752 (laccase-7), Eucgr.B03985 (transcription factor MYB108), Eucgr.D00536 (GDSL esterase/lipase At5g45920) and Eucgr.B02347 (scarecrow-like protein 34). These 51 genes might be associated with the high propagation ability of Eucalyptus and 22 might be induced after the dedifferentiation. Last, we performed WGCNA to identify the co-expressed genes during the callus development of Eucalyptus and qRT-PCR experiment to validate the gene expression patterns. Conclusions: This is the first time to globally study the gene profiles during the callus development of Eucalyptus. The results will improve our understanding of gene regulation and molecular mechanisms in the callus maturation and shoot regeneration.

Aquaporins such as the plasma membrane intrinsic proteins (PIPs) allow water to move through cell membranes and are vital for stomatal movement in plants. Despite their importance, the dynamic changes in aquaporins during water efflux and influx have not been directly observed in real time in vivo. Here, to determine which factors regulate these changes during the bidirectional translocation of water, we examined aquaporin dynamics during the stomatal immune response to the bacterial flagellin-derived peptide flg22. The Arabidopsis (Arabidopsis thaliana) aquaporin mutant pip2;1 showed defects in the flg22-induced stomatal response. Variable-angle total internal reflection fluorescence microscopy revealed that the movement dynamics and dwell times of AQ6]GFP-AtPIP2;1 in guard cells and subsidiary cells exhibited cell type-specific dependencies on flg22. The cytoskeleton, rather than the cell wall, was the major factor regulating AtPIP2;1 dynamics, although both the cytoskeleton and cell wall might form bounded domains that restrict the diffusion of AtPIP2;1 in guard cells and subsidiary cells. Finally, our analysis revealed the different roles of cortical actin and microtubules in regulating AtPIP2;1 dynamics in guard cells, as well as subsidiary cells, under various conditions. Our observations shed light on the heterogeneous mechanisms that regulate membrane protein dynamics in plants in response to pathogens.

Ammopiptanthus, a unique evergreen broadleaf shrub endemic to the desert regions of Northwest China, exhibits a remarkable capacity for aeolian erosion control and dune stabilization. Attributed to its robust tolerance in terms of xerotolerance, halophytic adaptations, extreme thermotolerance, resistance to biotic and abiotic degradation and its defensive strategies against herbivory, Ammopiptanthus has emerged as an exemplary model organism for the study of plant resilience to diverse environmental stressors. Current research on Ammopiptanthus is scattered, lacking a systematic review, which poses a disadvantage for subsequent in-depth studies and the effective conservation of this endangered resource. In recent years, natural Ammopiptanthus communities have been severely disrupted, and the species’ natural range is rapidly shrinking. Here, this review summarizes the signaling pathways in the Ammopiptanthus response to biotic stress (especially the early signaling events), as well as the research advances in the resistance interactions between biotic and abiotic stresses. Then, the synergistic effects of multiple environmental pressures on Ammopiptanthus could be established, which may provide guidance for further studies on the resistance mechanism of Ammopiptanthus and be beneficial to its natural community protection and reconstruction.

Background: Somatic embryogenesis (SE) was recognized as an important tool for plants to propagate. However, our knowledge about the proteins involved in early SE including the callus dedifferentiation is still limited, especially in the economic woody tree – Eucalyptus. Results: We used the data-independent acquisition mass-spectrometry to study the different proteome profiles of early SE of two Eucalyptus species—E. camaldulensis (high regeneratively potential) and E. grandis x urophylla (low regenerative potential). Initially, 35,207 peptides and 7,077 proteins were identified in the stem and tissue-culture induced callus of the two Eucalyptus species. MSstat identified 2,078 and 2,807 differentially expressed proteins (DEPs) in early SE of E. camaldulensis and E. grandis x urophylla, respectively. They shared 760 upregulated and 420 downregulated proteins, including 4 transcription factors, 31 ribosomal proteins, 1 histone, 3 zinc finger proteins (ZFPs), 16 glutathione transferases, 10 glucosyltransferases, ARF19, WOX8 and PIN1. These proteins might be involved in the early SE of Eucalyptus. By combining the miRNA and RNA-Seq results, some miRNA ~ gene/protein regulatory networks were identified in early SE of Eucalyptus, such as miR160 ~ TPP2, miR164 ~ UXS2, miR169 ~ COX11 and miR535 ~ Eucgr.E01067. Further, we found SERK, WRKY, ZFP and ABC transporter might be related with high SE potential. Conclusions: Overall, our study identified proteins involved in the early SE and related to the high regeneration potential of Eucalyptus. It greatly enhanced our understanding of the early SE and the SE capacity of Eucalyptus.

The WRKY family of transcription factors plays important roles in plant growth and responses to biotic and abiotic stresses. Ammopiptanthus nanus, the only evergreen broadleaf shrub endemic to the desert and semi-desert regions of northwestern China, is highly tolerant to various stresses. However, a systematic study of WRKY proteins in A. nanus has not been reported. In the present study, we identified 63 WRKY genes in the A. nanus genome. Based on the conserved WRKY domains, zinc finger structures, and phylogenetic relationships in their encoded proteins, we classified these genes into four groups (group I–IV) and several subgroups (subgroup IIa–IIe). Conserved motif analysis showed that all motifs except those within the WRKY domains had a subfamily-specific distribution. Expression analysis revealed that the AnWRKY genes had distinct expression patterns, with some being more responsive to herbivory and drought stresses than others. Based on the results of our current study, we speculate that AnWRKY40 and AnWRKY48 are positive regulators of the plant’s response to drought and herbivory stresses, respectively. Our results indicate that AnWRKY genes contribute to the ability of A. nanus plants to withstand harsh, dry conditions.