Successful floral meristem (FM) determinacy is critical for subsequent reproductive development and the plant life cycle. Although the phytohormones cytokinin and auxin interact to coregulate many aspects of plant development, whether and how cytokinin and auxin function in FM determinacy remain unclear. Here, we show that in Arabidopsis thaliana, cytokinin homeostasis is critical for FM determinacy. In this developmental context, auxin promotes the expression of AUXIN RESPONSE FACTOR3 (ARF3) to repress cytokinin activity. ARF3 directly represses the expression of ISOPENTENYLTRANSFERASE (IPT) family genes and indirectly represses LONELY GUY (LOG) family genes, both of which encode enzymes required for cytokinin biosynthesis. ARF3 also directly inhibits the expression of ARABIDOPSIS HISTIDINE KINASE4, a cytokinin receptor gene, resulting in reduced cytokinin activity. Consequently, ARF3 controls cell division by regulating cell cycle gene expression through cytokinin. In flowers, we show that AGAMOUS (AG) dynamically regulates the expression of ARF3 and IPTs, resulting in coordinated regulation of FM maintenance and termination through cell division. Moreover, genome-wide transcriptional profiling revealed both repressive and active roles for ARF3 in early flower development. Our findings establish a molecular link between AG and auxin/cytokinin and shed light on the mechanisms of stem cell maintenance and termination in the FM.

Fusarium wilt disease poses a severe threat to watermelon cultivation by affecting the yield and quality of the fruit. We had previously found that the rhizosphere microbiome has a significant impact on the ability of watermelon plants to resist Fusarium wilt development and that salicylic acid (SA) is closely related to this phenomenon. Therefore, in this study, the role of SA as a mediator between plants and microbes in activating resistance against Fusarium oxysporum f. sp. niveum (FON) infection was explored through physiological, biochemical, and metagenomic sequencing experiments. We demonstrated that exogenous SA treatment could specifically increase some beneficial rhizosphere species that can confer resistance against FON inoculation, such as Rhodanobacter, Sphingomonas, and Micromonospora. Functional annotation analysis indicated that SA application significantly increased the relative abundance of glycoside hydrolase and polysaccharide lyase genes in the microbiome, which may play an essential role in increasing plant lipids. Moreover, network interaction analysis suggested that the highly expressed AAC6_IIC gene may be manipulated through SA signal transduction pathways. In conclusion, these results provide a novel strategy for controlling Fusarium wilt in watermelons from the perspective of environmental ecology, that is, by manipulating the rhizosphere microbiome through SA to control Fusarium wilt.

Fusarium wilt disease is one of the major diseases causing a decline in watermelon yield and quality. Researches have informed that phytohormones play essential roles in regulating plants growth, development, and stress defendants. However, the molecular mechanism of salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA) in resistance to watermelon Fusarium wilt remains unknown. In this experiment, we established the SA, JA, and ABA determination system in watermelon roots, and analyzed their roles in against watermelon Fusarium wilt compared to the resistant and susceptible varieties using transcriptome sequencing and RT-qPCR. Our results revealed that the up-regulated expression of Cla97C09G174770, Cla97C05G089520, Cla97C05G081210, Cla97C04G071000, and Cla97C10G198890 genes in resistant variety were key factors against (Fusarium oxysporum f. sp. Niveum) FON infection at 7 dpi. Additionally, there might be crosstalk between SA, JA, and ABA, caused by those differentially expressed (non-pathogen-related) NPRs, (Jasmonate-resistant) JAR, and (Pyrabactin resistance 1-like) PYLs genes, to trigger the plant immune system against FON infection. Overall, our results provide a theoretical basis for watermelon resistance breeding, in which phytohormones participate.

Premature senescence of leaves causes a reduced yield and quality of rice by affecting plant growth and development. The regulatory mechanisms underlying early leaf senescence are still unclear. The Leaf senescence 1 (LS1) gene encodes a C2H2-type zinc finger protein that is localized to both the nucleus and cytoplasm. In this study, we constructed a rice mutant named leaf senescence 1 (ls1) with a premature leaf senescence phenotype using CRISPR/Cas9-mediated editing of the LS1 gene. The ls1 mutants exhibited premature leaf senescence and reduced chlorophyll content. The expression levels of LS1 were higher in mature or senescent leaves than that in young leaves. The contents of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) were significantly increased and catalase (CAT) activity was remarkably reduced in the ls1 plants. Furthermore, a faster decrease in pigment content was detected in mutants than that in WT upon induction of complete darkness. TUNEL and staining experiments indicated severe DNA degradation and programmed cell death in the ls1 mutants, which suggested that excessive ROS may lead to leaf senescence and cell death in ls1 plants. Additionally, an RT-qPCR analysis revealed that most senescence-associated and ROS-scavenging genes were upregulated in the ls1 mutants compared with the WT. Collectively, our findings revealed that LS1 might regulate leaf development and function, and that disruption of LS1 function promotes ROS accumulation and accelerates leaf senescence and cell death in rice.

In this study, the LBD (Lateral Organ Boundaries Domain) gene family, a group of plant-specific transcription factors critical for plant growth and development as well as metabolic regulation, was comprehensively characterized in rice. We identified 36 LBD genes using multi-source genomic data and systematically classified them into Class I (31 genes) and Class II (5 genes). Analysis of their physicochemical properties revealed significant variations in amino acid length, molecular weight, isoelectric points, and hydropathicity. Motif analysis identified conserved LOB domains and other motifs potentially linked to functional diversity. Cis-acting element analysis indicated the involvement of these genes in various biological processes, including light response, hormone signaling, and stress response. Expression profiling demonstrated tissue-specific expression patterns, with several genes, such as XM_015770711.2, XM_015776632.2, and XM_015792766.2, showing relatively high expression in rice roots, implying their important role in root development. Transcriptome data further supported the involvement of specific genes in responses to phytohormones such as jasmonic acid (JA) and abscisic acid (ABA), as well as environmental stresses like cold and drought. Notably, XM_015770711.2, XM_015776632.2, and XM_015772758.2 may contribute to the regulation of rice environmental adaptability by mediating ABA and JA signaling pathways, respectively. In conclusion, this study identified members of the LBD gene family through the screening of two rice gene databases, and performed a comprehensive analysis of their physicochemical properties, evolutionary relationships, and expression profiles under various conditions. These findings provided valuable insights for further functional studies of LBD genes. Moreover, this study provides a foundation for targeting LBD genes to enhance stress resilience (e.g., drought/cold tolerance) and root architecture optimization. The LBD gene family possesses dual values in both stress resistance regulation and developmental optimization. The construction of its multidimensional functional map lays the theoretical and resource foundation for the precise design of high-yield and stress-resistant varieties.

The bacteria pathogen Xanthomonas oryzae pv. oryzae (Xoo) infects rice and causes the severe disease of rice bacteria blight. As the central regulator of the salic acid (SA) signaling pathway, NPR1 is responsible for sensing SA and inducing the expression of pathogen-related (PR) genes in plants. Overexpression of OsNPR1 significantly increases rice resistance to Xoo. Although some downstream rice genes were found to be regulated by OsNPR1, how OsNPR1 affects the interaction of rice-Xoo and alters Xoo gene expression remains unknown. In this study, we challenged the wild-type and OsNPR1-OE rice materials with Xoo and performed dual RNA-seq analyses for the rice and Xoo genomes simultaneously. In Xoo-infected OsNPR1-OE plants, rice genes involved in cell wall biosynthesis and SA signaling pathways, as well as PR genes and nucleotide-binding site-leucine-rich repeat (NBS-LRR) genes, were significantly upregulated compared to rice variety TP309. On the other hand, Xoo genes involved in energy metabolism, oxidative phosphorylation, biosynthesis of primary and secondary metabolism, and transportation were repressed. Many virulence genes of Xoo, including genes encoding components of type III and other secretion systems, were downregulated by OsNPR1 overexpression. Our results suggest that OsNPR1 enhances rice resistance to Xoo by bidirectionally regulating gene expression in rice and Xoo.