Spatial transcriptomics reveals light-induced chlorenchyma cells involved in promoting shoot regeneration in tomato callus.

Callus is a reprogrammed cell mass involved in plant regeneration and gene transformation in crop engineering. Pluripotent callus cells develop into fertile shoots through shoot regeneration. The molecular basis of the shoot regeneration process in crop callus remains largely elusive. This study pioneers the exploration of the spatial transcriptome of tomato callus during shoot regeneration. The findings reveal the presence of highly heterogeneous cell populations within the callus, including epidermis, vascular tissue, shoot primordia, inner callus, and outgrowth shoots. By characterizing the spatially resolved molecular features of shoot primordia and surrounding cells, specific factors essential for shoot primordia formation are identified. Notably, chlorenchyma cells, enriched in photosynthesis-related processes, play a crucial role in promoting shoot primordia formation and subsequent shoot regeneration. Light is shown to promote shoot regeneration by inducing chlorenchyma cell development and coordinating sugar signaling. These findings significantly advance our understanding of the cellular and molecular aspects of shoot regeneration in tomato callus and demonstrate the immense potential of spatial transcriptomics in plant biology.

Correction: Synergistic effect of polysaccharides and flavonoids on lipid and gut microbiota in hyperlipidemic rats.

Correction for 'Synergistic effect of polysaccharides and flavonoids on lipid and gut microbiota in hyperlipidemic rats' by Yun-fei Bai et al., Food Funct., 2023, 14, 921-933, https://doi.org/10.1039/D2FO03031D.

Synergistic effect of polysaccharides and flavonoids on lipid and gut microbiota in hyperlipidemic rats.

Hyperlipidemia is a global health risk factor, and its development is closely related to the absorption and metabolism of lipids in the intestine. In this study, the Auricularia auricula polysaccharide, the Tremella polysaccharide, and hawthorn flavonoids were mixed by equal weight (HDC), and then its effect on the intervention in the intestine and blood lipids of hyperlipidemic rats on a high-fat diet (HFD) was investigated. The results revealed that HDC significantly inhibited the development of hyperlipidemia and reduced lipid levels and fat accumulation. In addition, HDC improved the edema deformation of intestinal epithelial cells, impaired the intestinal barrier induced by HFD, and improved the antioxidant capacity of the intestine. HDC showed a significant synergistic effect. Analysis of the gut microbiota by 16s rRNA gene sequencing showed that HDC reduced the ratio of Bacteroidetes/Firmicutes and the relative abundance of actinomycetes. At the genus level, the relative abundance of Lactobacillus, Rumincococcaceae-UCG-14, and Muribaculaceae was increased and the relative abundance of Allobaculum, Corynebacterium-1, Blautia, and Turicibucter was decreased. Intestinal lipidomics showed that HDC reduced the levels of DGDG, LPE, PG, phSM, PIP2, SoG1, and SM in the intestine of HFD rats, although there were no significant differences in LPE, PG, and phSM. 42 HDC-acting lipid biomarkers were screened. In conclusion, these findings support the potential of HDC intervention to prevent hyperlipidemia by regulating gut microbiota and lipid absorption and metabolism in the intestine.

The receptor kinase OsWAK11 monitors cell wall pectin changes to fine-tune brassinosteroid signaling and regulate cell elongation in rice.

Rates of plant cell elongation change with day-night alternation, reflecting differences in metabolism related to cell wall remodeling. Information from cell wall surveillance pathways must be integrated with growth regulation pathways to provide feedback regulation of cell wall modification; such feedback regulation is important to ensure sufficient strength and prevent rupture of the cell wall during growth. Several lines of evidence suggest that cell wall perturbations often influence phytohormone signaling, but the identity of the nexus between these two processes remained elusive. Here, we show that wall-associated kinase11 (OsWAK11) acts as a linker connecting cell wall pectin methyl-esterification changes and brassinosteroid (BR) signaling in rice. Our data show that OsWAK11 controls several important agronomical traits by regulating cell elongation in rice. OsWAK11 directly binds and phosphorylates the BR receptor OsBRI1 at residue Thr752, within a motif conserved across most monocot graminaceous crops, thus hindering OsBRI1 interaction with its co-receptor OsSERK1/OsBAK1 and inhibiting BR signaling. The extracellular domain of OsWAK11 shows a much stronger interaction toward methyl-esterified pectin as compared with de-methyl-esterified pectin. OsWAK11 is stabilized in light but is degraded in darkness, in a process triggered by changes in the ratio of methyl-esterified to de-methyl-esterified pectin, creating fluctuations in plant BR signaling in response to day and night alternation. We conclude that OsWAK11 is a cell wall monitor that regulates cell elongation rates to adapt to the environment from the outside in, which complements the well-established inside-out signaling pathway affecting cell elongation in plants.

Overexpression of Lectin Receptor-Like Kinase 1 in Tomato Confers Resistance to Fusarium oxysporum f. sp. Radicis-Lycopersici.

The disease Fusarium crown and root rot (FCRR), caused mainly by Fusarium oxysporum f. sp. radicis-lycopersici (FORL), seriously affects commercial tomato [Solanum lycopersicum (Sl)] yields. However, the genes that offer resistance to FORL are limited and the mechanism of resistance to FCRR is poorly understood. Lectin receptor-like kinases (LecRKs) play critical roles in defensive responses and immunity in many plant species; however, whether specific LecRKs are involved in the response of tomato plants to FORL is unclear. Here, we report that the expression of SlLecRK1/Solyc09g011070.1 was obviously induced by the infection of FORL. Biochemical and cell biological data revealed that SlLecRK1 is an active kinase that is located at the cell membrane, while real-time quantitative PCR data suggested that SlLecRK1 is mainly expressed in stems and roots. Genetic studies showed that overexpression of SlLecRK1 significantly improved the resistance of tomato plants to FORL but did not cause visible changes in plant growth and development compared with wild-type control plants. RNA-Seq data suggested that the positive effects of SlLecRK1 on the resistance of tomato plants to FORL occur mainly by triggering the expression of ethylene-responsive transcription factor (ERF) genes. Together, our findings not only identify a new target for the development of FCRR-resistant tomato varieties, they also demonstrate a molecular mechanism linking SlLecRK1 and ERFs in regulating the immune responses of tomato plants to FORL.

Receptor-like kinase OsCR4 controls leaf morphogenesis and embryogenesis by fixing the distribution of auxin in rice.

Cell differentiation is a key event in organ development; it involves auxin gradient formation, cell signaling, and transcriptional regulation. Yet, how these processes are orchestrated during leaf morphogenesis is poorly understood. Here, we demonstrate an essential role for the receptor-like kinase OsCR4 in leaf development. oscr4 loss-of-function mutants displayed short shoots and roots, with tiny, crinkly, or even dead leaves. The delayed outgrowth of the first three leaves and seminal root in oscr4 was due to defects in plumule and radicle formation during embryogenesis. The deformed epidermal, mesophyll, and vascular tissues observed in oscr4 leaves arose at the postembryo stage; the corresponding expression pattern of proOsCR4:GUS in embryos and young leaves suggests that OsCR4 functions in these tissues. Signals from the auxin reporter DR5rev:VENUS were found to be altered in oscr4 embryos and disorganized in oscr4 leaves, in which indole-3-acetic acid accumulation was further revealed by immunofluorescence. OsWOX3A, which is auxin responsive and related to leaf development, was activated extensively and ectopically in oscr4 leaves, partially accounting for the observed lack of cell differentiation. Our data suggest that OsCR4 plays a fundamental role in leaf morphogenesis and embryogenesis by fixing the distribution of auxin.

Mutual Regulation of Receptor-Like Kinase SIT1 and B'κ-PP2A Shapes the Early Response of Rice to Salt Stress.

The receptor-like kinase SIT1 acts as a sensor in rice (Oryza sativa) roots, relaying salt stress signals via elevated kinase activity to enhance salt sensitivity. Here, we demonstrate that Protein Phosphatase 2A (PP2A) regulatory subunit B'κ constrains SIT1 activity under salt stress. B'κ-PP2A deactivates SIT1 directly by dephosphorylating the kinase at Thr515/516, a salt-induced phosphorylation site in the activation loop that is essential for SIT1 activity. B'κ overexpression suppresses the salt sensitivity of rice plants expressing high levels of SIT1, thereby contributing to salt tolerance. B'κ functions in a SIT1 kinase-dependent manner. During early salt stress, activated SIT1 phosphorylates B'κ; this not only enhances its binding with SIT1, it also promotes B'κ protein accumulation via Ser502 phosphorylation. Consequently, by blocking SIT1 phosphorylation, B'κ inhibits and fine-tunes SIT1 activity to balance plant growth and stress adaptation.

Simple and rapid determination of N(6)-(Δ(2)-isopentenyl)adenine, zeatin, and dihydrozeatin in plants using on-line cleanup liquid chromatography coupled with hybrid quadrupole-Orbitrap high-resolution mass spectrometry.

A simple and rapid method was developed for the determination of three free cytokinins, namely, N(6)-(Δ(2)-isopentenyl)adenine, zeatin, and dihydrozeatin, in plants using TurboFlow on-line cleanup liquid chromatography combined with hybrid quadrupole-Orbitrap high-resolution mass spectrometry. The samples were extracted using acetonitrile, and then the extract was purified on a C18-p column, in which the sample matrix was removed and the analytes were retained. Subsequently, the analytes were eluted from the extraction column onto the analytical column (Hypersil Gold C18 column) prior to chromatographic separation and hybrid Q-Orbitrap detection using the targeted-MS(2) scan mode. The linearity was satisfactory with a correlation coefficient of >0.999 at concentrations ranging from 5-5000 pg/mL. The limits of quantification for the analytes ranged from 4.2-5.2 pg/mL. The intra- and inter-day average recoveries of analytes fortified at three levels ranged from 85.4-108.2%, and the intra- and inter-day relative standard deviations ranged from 4.04-8.57%. The method was successfully applied for the determination of free cytokinins in different tissue samples of Oryza sativa and Arabidopsis thaliana.

LNK1 and LNK2 are transcriptional coactivators in the Arabidopsis circadian oscillator.

Transcriptional feedback loops are central to the architecture of eukaryotic circadian clocks. Models of the Arabidopsis thaliana circadian clock have emphasized transcriptional repressors, but recently, Myb-like REVEILLE (RVE) transcription factors have been established as transcriptional activators of central clock components, including PSEUDO-RESPONSE REGULATOR5 (PRR5) and TIMING OF CAB EXPRESSION1 (TOC1). We show here that NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED1 (LNK1) and LNK2, members of a small family of four LNK proteins, dynamically interact with morning-expressed oscillator components, including RVE4 and RVE8. Mutational disruption of LNK1 and LNK2 function prevents transcriptional activation of PRR5 by RVE8. The LNKs lack known DNA binding domains, yet LNK1 acts as a transcriptional activator in yeast and in planta. Chromatin immunoprecipitation shows that LNK1 is recruited to the PRR5 and TOC1 promoters in planta. We conclude that LNK1 is a transcriptional coactivator necessary for expression of the clock genes PRR5 and TOC1 through recruitment to their promoters via interaction with bona fide DNA binding proteins such as RVE4 and RVE8.

[Clinical study of submental artery island myocutaneous flap for reconstruction of oral and maxillofacial defects following operation].

OBJECTIVE: To evaluate the outcome and indication of the reconstruction of oral and maxillofacial postoperative defects by submental artery island myocutaneous flaps. METHODS: Sixty eight cases with the reconstruction of oral and maxillofacial defects by submental artery island myocutaneous flaps from January 2006 to May 2010 were analysed retrospectively. Primary lesions included carcinomas originating from tongue (28 cases), palate (13 cases), mouth floor (9 cases), gingiva (4 cases), buccal mucosa (6 cases), lip (3 cases), and other malignant or benign tumors (5 cases). The ages ranged from 25 to 84 years (mean 58 years); 47 males and 21 females. The sizes of skin paddle varied from a minimum of 4 cm × 4 cm to a maximum of 15 cm × 10 cm. RESULTS: Of the 68 flaps, 62 were survival, 4 had partial necrosis but healed with treatments, and 2 failed due to complete necrosis. Appearance and functions of recipient sites were satisfactory. The followed-up time was 3 - 24 months, local recurrence occurred in 5 cases and cervical lymph node metastases were found in 15 patients. CONCLUSION: Submental island flap is reliable for the reconstruction of postoperative defects in early oral cancer without regional lymph node metastasis or in benign tumor.