ZjSEP3 modulates flowering time by regulating the LHY promoter

CmHRE2L-CmACS6 transcriptional cascade negatively regulates waterlogging tolerance in Chrysanthemum

The role of ethylene as an initial signaling molecule in waterlogging stress is well-established. However, the complex molecular mechanisms underlying ethylene biosynthesis and its functional significance in chrysanthemums under waterlogging conditions have remained unclear. In this study, we observed an increase in the expression of 1-aminocyclopropane-1-carboxylate synthase 6 (CmACS6), which encodes a key enzyme responsible for ethylene biosynthesis, in response to waterlogging. This elevation increases ethylene production, induces leaf chlorosis, and enhances the chrysanthemum's sensitivity to waterlogging stress. Moreover, our analysis of upstream regulators revealed that the expression of CmACS6, in response to waterlogging, is directly upregulated by CmHRE2-like (Hypoxia Responsive ERF-like, CmHRE2L), an ethylene response factor. Notably, CmHRE2-L binds directly to the GCC-like motif in the promoter region of CmACS6. Genetic validation assays demonstrated that CmHRE2L was induced by waterlogging and contributed to ethylene production, consequently reducing waterlogging tolerance in a partially CmACS6-dependent manner. This study identified the regulatory module involving CmHRE2L and CmACS6, which governs ethylene biosynthesis in response to waterlogging stress.

Alternative splicing variants of IiSEP3 in Isatis indigotica are involved in floral transition and flower development

The SEPALLATA3 genes regulate several aspects of plant development. This study identified four distinct splicing isoforms of the SEPALLATA3 gene in Isatis indigotica (I. indigotica). IiSEP3-1 and IiSEP3-2 have eight exons and were named as IiSEP3-2/1. However, IiSEP3-3 and IiSEP3-4 with the missing sixth exon were labeled IiSEP3ΔK3. Furthermore, the IiSEP3-1 and IiSEP3-4 amino acids sequences lack the V90. IiSEP3 splicing variants were primarily expressed in floral organs, with petals showing the highest expression. Ectopic expression of IiSEP3-2 or IiSEP3-3 may cause early flowering and reduce the number of sepals, petals, and stamens. The ectopic expression of IiSEP3-2 resulted in cauline leaves and sepals converting to carpelloid structures. In contrast, the four floral whorls prematurely wilted, and the entire flower displayed an abortive state when IiSEP3-3 was expressed ectopically. Silencing the IiSEP3 gene of I. indigotica employing VIGS (tobacco rattle virus-mediated virus-induced gene silencing) technology using the TRV-IiSEP3-2/1 vector delayed flowering time and reduced the number of petals and stamens. Plants silenced with TRV-IiSEP3ΔK3 also exhibited similar phenotypes, including fewer sepals. The transcriptome analysis of silenced plants (TRV-IiSEP3-2/1 treatment group) indicated significant alterations in 1861 genes, with 1035 upregulated and 826 downregulated. TRV-IiSEP3ΔK3 treatment altered the expression of 2063 genes in plants, with 1289 genes upregulated and 774 genes transcription inhibited. Y2H and BIFC experiments revealed that IiSEP3-2 and IiSEP3-3 had distinct interacting proteins. Thus, we can conclude that IiSEP3-2 and IiSEP3-3 interact with different proteins, affecting floral transition and organ development in I. indigotica.

Overview of Repressive miRNA Regulation by Short Tandem Target Mimic (STTM): Applications and Impact on Plant Biology

The application of miRNA mimic technology for silencing mature miRNA began in 2007. This technique originated from the discovery of the INDUCED BY PHOSPHATE STARVATION 1 (IPS1) gene, which was found to be a competitive mimic that prevents the cleavage of the targeted mRNA by miRNA inhibition at the post-transcriptional level. To date, various studies have been conducted to understand the molecular mimic mechanism and to improve the efficiency of this technology. As a result, several mimic tools have been developed: target mimicry (TM), short tandem target mimic (STTM), and molecular sponges (SPs). STTM is the most-developed tool due to its stability and effectiveness in decoying miRNA. This review discusses the application of STTM technology on the loss-of-function studies of miRNA and members from diverse plant species. A modified STTM approach for studying the function of miRNA with spatial-temporal expression under the control of specific promoters is further explored. STTM technology will enhance our understanding of the miRNA activity in plant-tissue-specific development and stress responses for applications in improving plant traits via miRNA regulation.

Identification of MADS-Box Transcription Factors in Iris laevigata and Functional Assessment of IlSEP3 and IlSVP during Flowering

Iris laevigata is ideal for gardening and landscaping in northeast China because of its beautiful flowers and strong cold resistance. However, the short length of flowering time (2 days for individual flowers) greatly limits its applications. Molecular breeding and engineering hold high potential for producing I. laevigata of desirable flowering properties. A prerequisite is to identify and characterize key flowering control genes, the identity of which remains largely unknown in I. laevigata due to the lack of genome information. To fill this knowledge gap, we used sequencing data of the I. laevigata transcriptome to identify MADS-box gene-encoding transcription factors that have been shown to play key roles in developmental processes, including flowering. Our data revealed 41 putative MADS-box genes, which consisted of 8 type I (5 Mα and 3 Mβ, respectively) and 33 type II members (2 MIKC* and 31 MIKCC, respectively). We then selected IlSEP3 and IlSVP for functional studies and found that both are localized to the nucleus and that they interact physically in vitro. Ectopic expression of IlSEP3 in Arabidopsis resulted in early flowering (32 days) compared to that of control plants (36 days), which could be mediated by modulating the expression of FT, SOC1, AP1, SVP, SPL3, VRN1, and GA20OX. By contrast, plants overexpressing IlSVP were phenotypically similar to that of wild type. Our functional validation of IlSEP3 was consistent with the notion that SEP3 promotes flowering in multiple plant species and indicated that IlSEP3 regulates flowering in I. laevigata. Taken together, this work provided a systematic identification of MADS-box genes in I. laevigata and demonstrated that the flowering time of I. laevigata can be genetically controlled by altering the expression of key MADS-box genes.