Summary: Salt stress dramatically impedes plant growth and development as well as crop yield. The apple production regions are reduced every year, because of the secondary salt damage by improper fertilization and irrigation. To expand the cultivation area of apple (Malus domestica) and select salt‐resistant varieties, the mechanism of salt tolerance in apple is necessary to be clarified. The miR156/SPL regulatory module plays key roles in embryogenesis, morphogenesis, life cycle stage transformation, flower formation and other processes. However, its roles in the mechanisms of salt tolerance are unknown. In order to elucidate the mechanism of 156/SPL regulating salt stress in apple, we performed RLM‐5’ RACE and stable genetic transformation technology to verify that both mdm‐MIR156a and MdSPL13 responded to salt stress in apple and that the latter was the target of the former. MIR156a overexpression weakened salt resistance in apple whereas MdSPL13 overexpression strengthened it. A total of 6094 differentially expressed genes relative to nontransgenic apple plants were found by RNA‐Seq analysis of MdSPL13OE. Further verification indicated that MdSPL13 targeted the MdWRKY100 gene promoter. Moreover, MdWRKY100 overexpression enhanced salt tolerance in apple. Our results revealed that the miR156/SPL module regulates salt tolerance by up‐regulating MdWRKY100 in apple. This study is the first to elucidate the mechanism underlying the miRNA network response to salt stress in apple and provides theoretical and empirical bases and genetic resources for the molecular breeding of salt tolerance in apple.

G-protein signaling and brassinosteroid (BR) phytohormones play important roles in regulating rice (Oryza sativa) yield-related plant architecture, such as leaf inclination and grain size. However, the relationship between G-proteins and BR signaling has not been fully elucidated in rice. The present study indicates that the G-protein Gγ subunit DENSE AND ERECT PANICLE 1 (DEP1) positively regulates BR signaling in rice and that BRs promote DEP1 nuclear entry through GRAIN NUMBER ASSOCIATED (GNA). Additionally, DEP1 interacts with and acts upstream of OsMYB86, an R2R3-MYB family transcription factor that positively regulates BR signaling by directly binding to the promoter of its downstream gene BRASSINOSTEROID UPREGULATED 1 (BU1), activating its expression in rice. In the nucleus, DEP1 interacts with OsMYB86 and GNA, significantly enhancing OsMYB86-mediated activation of BU1 expression. Furthermore, BU1 interacts with another HLH protein, INCREASED LEAF INCLINATION1 (ILI1), and a bHLH protein, ILI1 BINDING bHLH (IBH1). Interaction between ILI1 and BU1 facilitates translocation of BU1 from the cytoplasm to the nucleus, where they impede IBH1 binding to the promoter of the AUXIN RESPONSE FACTOR 11 (OsARF11) gene, which is involved in crosstalk between BR and auxin, thus effectively relieving the IBH1-repressed transcription of OsARF11. These findings reveal a DEP1-mediated signaling pathway that links G-proteins to the traditional BR signaling pathway, ensuring the efficient activation of BR responses in rice.

The development of the horticultural industry is largely limited by disease and excessive pesticide application. MicroRNAs constitute a major portion of the transcriptomes of eukaryotes. Various microRNAs have been recognized as important regulators of the expression of genes involved in essential biological processes throughout the whole life cycle of plants. Recently, small RNA sequencing has been applied to study gene regulation in horticultural plants. In this review, we summarize the current understanding of the biogenesis and contributions of microRNAs in horticultural plant disease resistance. These microRNAs may potentially be used as genetic resources for improving disease resistance and for molecular breeding. The challenges in understanding horticultural plant microRNA biology and the possibilities to make better use of these horticultural plant gene resources in the future are discussed in this review.

Graft healing involves a series of cytological and molecular events including wound responses, callus formation and vascular bundle remodelling. Hormones are important signalling molecules regulating plant development and responses to environmental stimuli. However, the detailed dynamics of phytohormones in graft healing remain elusive. In this research, internodes above and below the graft site were harvested from 0 to 168 hours after grafting (HAG), and liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to determinate jasmonic acid, auxin, cytokinin, ethylene, salicylic acid, abscisic acid and gibberellin levels during the graft healing process. Uniform manifold approximation and projection (UMAP) and k-means analyses were performed to explore hormone spatio-temporal dynamics. We found the stage-specific and asymmetric accumulation of phytohormones in the tomato graft healing process. At the early healing stage (before vascular bundle reconnection), IAA, cZ, ABA, JA and SA mainly accumulated above the graft site, while tZ and ACC mainly accumulated below the graft site. MEIAA, ICAld and IP mainly accumulated at the later stage. Comminated with the healing process, we suggested that JA is mainly involved in wound responses, IAA is beneficial to the formation of callus and vascular cell development, tZ promotes cell division, and IP is linked to vascular bundle remodelling. In addition, expression of JA-related genes SlMYC2 and SlJAZ2, IAA-related gene SlIAA1, tZ-related genes SlHP2 and SlRR8, and IP-related gene SlRR9 correlated with hormone accumulation. The findings provide important information about the hormones and genes involved in the tomato graft healing process.