Knox homologs shoot meristemless (STM) and KNAT6 are epistatic to CLAVATA3 (CLV3) during shoot meristem development in Arabidopsis thaliana

The GhWL1-GhH1-GhGA2OX1 Transcriptional Module Regulates Cotton Leaf Morphology

Leaf morphology critically influences photosynthetic efficiency, directly affecting crop yield and quality. In this study, a T-DNA insertion mutant (wl-D), characterized by a wrinkled-leaf phenotype, is identified. Genetic analysis reveals that this phenotype is governed by a single dominant gene, WRINKLED-LEAF 1 (GhWL1), which is highly expressed in wl-D compared to the wild type (WT). Overexpression of GhWL1 in WT caused curling at leaf edges, while suppression of GhWL1 in wl-D restored normal leaf morphology, validating its functional role. Further analysis demonstrated that GhWL1 interacts with GhH1, a protein with a KNOX1 structural domain, to regulate leaf development. Overexpression of GhH1 in WT results in a leaf shrinkage phenotype similar to wl-D, whereas suppressing GhH1 in wl-D restored normal leaf morphology, indicating that GhH1 acts downstream of GhWL1. The GhWL1-GhH1 complex directly binds to the promoter of GhGA2OX1 (gibberellin 2-beta-dioxygenase 1), positively regulating its expression. Overexpression of GhGA2OX1 in WT mimicked the leaf shrinkage phenotype observed in plants overexpressing GhH1. These findings establish the GhWL1-GhH1-GhGA2OX1 module as a critical pathway in regulating leaf development, offering valuable insights into the genetic and hormonal networks controlling leaf morphological diversity.

Profiling of Known and Novel microRNAs in an Oleaginous Crop Native to the Amazon Basin, Sacha Inchi (Plukenetia volubilis), Through smallRNA-Seq

BACKGROUND

MicroRNAs (miRNAs) play crucial roles in regulating tissue-specific gene expression and plant development. This study explores the identification and functional characterization of miRNAs in Plukenetia volubilis (sacha inchi), an economically and nutritionally significant crop native to the Amazon basin, across three organs: root, stem, and leaf.

METHODS

Small RNA libraries were sequenced on the Illumina Novaseq 6000 platform, yielding high-quality reads that facilitated the discovery of known and novel miRNAs using miRDeep-P.

RESULTS

A total of 277 miRNAs were identified, comprising 71 conserved and 206 novel miRNAs, across root, stem, and leaf tissues. In addition, differential expression analysis using DESeq2 identified distinct miRNAs exhibiting tissue-specific regulation. Notably, novel miRNAs like novel_1, novel_88, and novel_189 showed significant roles in processes such as auxin signaling, lignin biosynthesis, and stress response. Functional enrichment analysis of miRNA target genes revealed pathways related to hormonal regulation, structural reinforcement, and environmental adaptation, highlighting tissue-specific functions. The Principal Component Analysis and PERMANOVA confirmed clear segregation of miRNA expression profiles among tissues, underlining organ-specific regulation. Differential expression patterns emphasized unique regulatory roles in each organ: roots prioritized stress response and nutrient uptake, leaves focused on photosynthesis and UV protection, and stems contributed to structural integrity and nutrient transport, suggesting evolutionary adaptations in P. volubilis.

CONCLUSIONS

This study identified novel miRNA-mediated networks that regulate developmental and adaptive processes in P. volubilis, underscoring its molecular adaptations for resilience and productivity. By characterizing both conserved and novel miRNAs, the findings lay a foundation for genetic improvement and molecular breeding strategies aimed at enhancing agronomic traits, stress tolerance, and the production of bioactive compounds.

Genetic Analysis and Fine Mapping of QTL for the Erect Leaf in Mutant mths29 Induced through Fast Neutron in Wheat

The erect leaf plays a crucial role in determining plant architecture, with its growth and development regulated by genetic factors. However, there has been a lack of comprehensive studies on the regulatory mechanisms governing wheat lamina joint development, thus failing to meet current breeding demands. In this study, a wheat erect leaf mutant, mths29, induced via fast neutron mutagenesis, was utilized for QTL fine mapping and investigation of lamina joint development. Genetic analysis of segregating populations derived from mths29 and Jimai22 revealed that the erect leaf trait was controlled by a dominant single gene. Using BSR sequencing and map-based cloning techniques, the QTL responsible for the erect leaf trait was mapped to a 1.03 Mb physical region on chromosome 5A. Transcriptome analysis highlighted differential expression of genes associated with cell division and proliferation, as well as several crucial transcription factors and kinases implicated in lamina joint development, particularly in the boundary cells of the preligule zone in mths29. These findings establish a solid foundation for understanding lamina joint development and hold promise for potential improvements in wheat plant architecture.

Stem Cells: Engines of Plant Growth and Development

The development of both animals and plants relies on populations of pluripotent stem cells that provide the cellular raw materials for organ and tissue formation. Plant stem cell reservoirs are housed at the shoot and root tips in structures called meristems, with the shoot apical meristem (SAM) continuously producing aerial leaf, stem, and flower organs throughout the life cycle. Thus, the SAM acts as the engine of plant development and has unique structural and molecular features that allow it to balance self-renewal with differentiation and act as a constant source of new cells for organogenesis while simultaneously maintaining a stem cell reservoir for future organ formation. Studies have identified key roles for intercellular regulatory networks that establish and maintain meristem activity, including the KNOX transcription factor pathway and the CLV-WUS stem cell feedback loop. In addition, the plant hormones cytokinin and auxin act through their downstream signaling pathways in the SAM to integrate stem cell activity and organ initiation. This review discusses how the various regulatory pathways collectively orchestrate SAM function and touches on how their manipulation can alter stem cell activity to improve crop yield.

BrCWM Mutation Disrupted Leaf Flattening in Chinese Cabbage (Brassica rapa L. ssp. pekinensis)

Leaf flattening plays a vital role in the establishment of plant architecture, which is closely related to plant photosynthesis and, thus, influences the product yield and quality of Chinese cabbage. In this study, we used the doubled haploid line ‘FT’ of Chinese cabbage as the wild type for ethyl methanesulfonate (EMS) mutagenesis and obtained a mutant cwm with stably inherited compact and wrinkled leaves. Genetic analysis revealed that the mutated trait was controlled by a single recessive nuclear gene, Brcwm. Brcwm was preliminarily mapped to chromosome A07 based on bulked segregant RNA sequencing (BSR-seq) and fine-mapped to a 205.66 kb region containing 39 genes between Indel12 and Indel21 using SSR and Indel analysis. According to the whole-genome re-sequencing results, we found that there was only one nonsynonymous single nucleotide polymorphism (SNP) (C to T) within the target interval on exon 4 of BraA07g021970.3C, which resulted in a proline to serine amino acid substitution. The mutated trait co-segregated with the SNP. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) revealed that BraA07g021970.3C expression was dramatically higher in ‘FT’ leaves than that in cwm leaves. BraA07g021970.3C is homologous to AT3G55000 encoding a protein related to cortical microtubule organization. A similar phenotype of dwarfism and wrinkled leaves was observed in the recessive homozygous mutant cwm-f1 of AT3G55000, and its T3 transgenic lines were restored to the Arabidopsis wild-type phenotype through ectopic overexpression of BraA07g021970.3C. These results verified that BraA07g021970.3C was the target gene essential for leaf flattening in Chinese cabbage.

Targeted mutagenesis of BnaSTM leads to abnormal shoot apex development and cotyledon petiole fusion at the seedling stage in Brassica napus L

The Arabidopsis homeodomain transcription factor SHOOT MERISTEMLESS (STM) is crucial for shoot apical meristem (SAM) function, which cooperates with CLAVATA3 (CLV3)/WUSCHEL (WUS) feedback regulation loops to maintain the homeostasis of stem cells in SAM. STM also interacts with the boundary genes to regulate the tissue boundary formation. However, there are still few studies on the function of STM in Brassica napus, an important oil crop. There are two homologs of STM in B. napus (BnaA09g13310D and BnaC09g13580D). In the present study, CRISPR/Cas9 technology was employed to create the stable site-directed single and double mutants of the BnaSTM genes in B. napus. The absence of SAM could be observed only in the BnaSTM double mutants at the mature embryo of seed, indicating that the redundant roles of BnaA09.STM and BnaC09.STM are vital for regulating SAM development. However, different from Arabidopsis, the SAM gradually recovered on the third day after seed germination in Bnastm double mutants, resulting in delayed true leaves development but normal late vegetative and reproductive growth in B. napus. The Bnastm double mutant displayed a fused cotyledon petiole phenotype at the seedling stage, which was similar but not identical to the Atstm in Arabidopsis. Further, transcriptome analysis showed that targeted mutation of BnaSTM caused significant changes for genes involved in the SAM boundary formation (CUC2, CUC3, LBDs). In addition, Bnastm also caused significant changes of a sets of genes related to organogenesis. Our findings reveal that the BnaSTM plays an important yet distinct role during SAM maintenance as compared to Arabidopsis.

Auxin-regulated timing of transition from vegetative to reproductive growth in rapeseed (Brassica napus L.) under different nitrogen application rates

Accelerating the differentiation of floral meristem (FM) from shoot apical meristems (SAM) which determines the conversion from vegetative to reproductive growth is of great significance for the production of rapeseed (Brassica napus L.). In this research, the mechanisms of different nitrogen (N) application rates (low N, N1; normal N, N2; and high N, N3) on different FM development stages triggering the regulation of FM differentiation genes through the auxin biosynthetic and signal transduction were investigated. We found that the stage of FM differentiation, which was identified through a stereomicroscope and scanning electron microscope, came 4 and 7 days earlier under high N rate than under normal and low N levels, with the seed yield increased by 11.1 and 22.6%, respectively. Analysis of the auxin and its derivatives contents showed that the main biosynthesis way of auxin was the indole acetaldehyde oxime (IAOx) pathway, with 3-Indole acetonitrile dramatically accumulated during FM differentiation. At the same time, an obvious decrease of IAA contents at each FM differentiation stage was detected, and then gradually rose. Results of the expression of genes involved in auxin biosynthesis, auxin signaling transduction, and FM identification under five FM differentiation stages and three nitrogen application rates showed that genes involved in auxin biosynthesis were regulated before the FM differentiation stage, while the regulation of FM identity genes appeared mainly at the middle and later periods of the five stages, and the regulation level of genes varied under different N rates. Taken together, a high nitrogen rate could accelerate the initiation of FM differentiation, and auxin involved a lot in this regulation.