Exploring the Role of TaPLC1-2B in Heat Tolerance at Seedling and Adult Stages of Wheat through Transcriptome Analysis.

Heat stress is a major abiotic stress that can cause serious losses of a crop. Our previous work identified a gene involved in heat stress tolerance in wheat, TaPLC1-2B. To further investigate its mechanisms, in the present study, TaPLC1-2B RNAi-silenced transgenic wheat and the wild type were comparatively analyzed at both the seedling and adult stages, with or without heat stress, using transcriptome sequencing. A total of 15,549 differentially expressed genes (DEGs) were identified at the adult stage and 20,535 DEGs were detected at the seedling stage. After heat stress, an enrichment of pathways such as phytohormones and mitogen-activated protein kinase signaling was mainly found in the seedling stage, and pathways related to metabolism, glycerophospholipid metabolism, circadian rhythms, and ABC transporter were enriched in the adult stage. Auxin and abscisic acid were downregulated in the seedling stage and vice versa in the adult stage; and the MYB, WRKY, and no apical meristem gene families were downregulated in the seedling stage in response to heat stress and upregulated in the adult stage in response to heat stress. This study deepens our understanding of the mechanisms of TaPLC1-2B in regard to heat stress in wheat at the seedling and adult stages.

Heterologous expression of the TaPI-PLC1-2B gene enhanced drought and salt tolerance in transgenic rice seedlings.

Drought and salt stress are important factors that affect plant growth and development and cause crop yield reductions worldwide. Phospholipase C is a class of enzymes that can hydrolyze phospholipids, and it has been shown to play an important role in plant growth regulation and stress response. We used rice as a model to investigate the function of the wheat TaPI-PLC1-2B gene in salt and drought tolerance. For this purpose, we heterologously expressed the TaPI-PLC1-2B gene in rice and studied the transcriptional differences in transgenic and wide-type rice plants in the presence and absence of drought and salt stress. Our results showed that 2130 and 1759 genes expressed differentially in the TaPI-PLC1-2B overexpression rice line under salt and drought stress, respectively. Gene ontology enrichment results showed that differentially expressed genes (DEGs) were significantly enriched in cellular process, metabolic process, stimulus-response, cell, organelle, catalytic activity, and other functional processes under salt and drought stress. In addition, the Kyoto Encyclopedia of Genes and Genomes pathway analysis showed DEG enrichment in plant-pathogen interaction, phosphoinositol, plant hormones, and other signaling pathways under the two stress treatments. Furthermore, the chromosomal localization of salt and drought stress-responsive DEGs showed a clear distribution pattern on specific rice chromosomes. For instance, the greatest number of drought stress-responsive genes mapped to rice chromosomes 1 and 6. The current analysis has built the basis for future explorations to decipher the TaPI-PLC1-2B-mediated plant stress response mechanism in the relatively challenging wheat system.

PPARγ/LXRα axis mediated phenotypic plasticity of lung fibroblasts in silica-induced experimental silicosis.

Silicosis is a disease mainly caused by pulmonary interstitial fibrosis caused by long-term inhalation of dust with excessively high content of free SiO2. Transdifferentiation of lung fibroblasts into myofibroblasts is an important cellular basis for silicosis, but the key transcription factors (TFs) involved in this process are still unclear. In order to explore the biological regulation of transcription factor PPARγ/LXRα in silica-induced pulmonary fibrosis, this study explored the molecular mechanism of PPARγ/LXRα involved in regulating transcription factors related to SiO2-induced lung injury at the cellular level and in animal models. ChIP-qPCR detected that PPARγ directly regulated the transcriptional activity of the LXRα gene promoter, while the PPARγ agonist RSG increased the expression of LXRα. In addition, we demonstrated in the cell model that upregulation of LXRα can inhibit silica-mediated fibroblast transdifferentiation, accompanied by an increase in the expression of SREBF1, PLTP and ABCA1. The results of LXRα silencing experiment matched those of overexpression experiment. These studies explored the role of LXRα in plasticity and phenotypic transformation between lung fibroblasts and myofibroblasts. Therefore, inhibiting or reversing the transdifferentiation of lung fibroblasts to myofibroblasts by intervening PPARγ/LXRα may provide a new therapeutic target for the treatment of silicosis.

Phosphoinositide-specific phospholipase C gene involved in heat and drought tolerance in wheat (Triticum aestivum L.).

BACKGROUND: Phosphoinositide-specific phospholipase C proteins mediate environmental stress responses in many plants. However, the potential of PI-PLC genes involved with abiotic stress tolerance in wheat remains un-explored. OBJECTIVE: To study TaPLC1 genetic relation with wheat drought and heat resistance. METHODS: The seedlings were treated with PI-PLC inhibitor U73122 at the single leaf stage. The seedlings were treated with drought and heat stress at the two leaf stage, and some physiological indexes and the expression profile of TaPLC1 gene were determined. And the TaPLC1 overexpression vector was transferred to Arabidopsis and selected to T3 generation for drought and heat stress treatment. RESULTS: After 4 h of drought and heat stress, the SOD activity, MDA and soluble sugar content of the two cultivars with inhibitor were higher than those without inhibitor, the chlorophyll content decreased. CS seedlings showed significant wilting phenomenon, and TAM107 showed slight wilting. After the elimination of drought and heat stress, all seedling wilting gradually recovered, while the leaf tips of the two varieties treated with inhibitors began to wilt and turn yellow, which was more significant 5 days after the drought and heat stress, while the degree of spring wilting and yellow in CS was earlier than that in TAM107. The expression patterns of TaPLC1 gene were different in the two cultivars, but the expression levels reached the maximum at 30 min of heat stress. The change of TaPLC1 expression in TAM107 without inhibitor treatment was significantly greater than that in CS. The expression level of TaPLC1 in the two cultivars under stress was significantly different between the two cultivars treated with inhibitor and untreated, and was lower than that of the normal plants under normal conditions. These results indicated that inhibition of TaPLC1 gene expression could enhance the sensitivity of seedlings to stress. In Arabidopsis, the root lengths of transgenic and wild-type seedlings were shortened after drought stress treatment, but the root lengths of transgenic plants decreased slightly. And the expression of TaPLC1 gene was significantly increased after drought and heat stress. This indicated that overexpression of TaPLC1 improved drought resistance of Arabidopsis. CONCLUSIONS: The results of this study suggest that TaPLC1 may be involved in the regulation mechanism of drought and heat stress in wheat.

miR-34a-5p Attenuates EMT through targeting SMAD4 in silica-induced pulmonary fibrosis.

Silicosis is an incurable occupational disease, and its pathological feature is diffuse pulmonary fibrosis. Pulmonary epithelial-mesenchymal transition (EMT) is one of the important events in the pathogenesis of silicosis. Previous studies found that abnormal expression of various microRNAs (miRNAs) involved in the development of lung fibrosis. However, their roles in silicosis have not been elucidated. To research the biological effects of miR-34a in EMT process in silica-induced lung fibrosis, we established the silicosis model in mouse and miR-34a intervention in a cell model of TGF-ß1 stimulated lung epithelial cells (A549). The results showed that miR-34a expression was down-regulated in the fibrotic lung tissue after silica treatment, and it was similarly expressed in A549 cells stimulated by TGF-ß1. Meanwhile, silica-induced EMT process can increase expression of two mesenchymal markers, α-SMA and vimentin. Furthermore, overexpression miR-34a markedly inhibited EMT stimulated by TGF-ß1. Mechanistically, SMAD4 was identified as the target of miR-34a. SMAD4 levels decreased in mRNA and protein levels in A549 cells upon miR-34a overexpression. In addition, the knockdown of SMAD4 blocked the EMT process. Taken together, miR-34a regulated EMT, which might be partially realized by targeting SMAD4. Our data might provide new insight into treatment targets for silica-induced pulmonary fibrosis.

Transcriptome analysis reveals a protective role of liver X receptor alpha against silica particle-induced experimental silicosis.

Silicosis, a severe and irreversible form of pulmonary fibrosis (PF) caused by long-term exposure to dust particles in production environments, is the biggest occupational health concern in China and most low-income countries. The transdifferentiation of pulmonary fibroblasts is the terminal event in silicosis, and specific transcription factors (TFs) play a crucial role in this condition. However, the relationship between TF-mediated regulation and silicosis remains unknown. We performed a transcriptomic analysis to elucidate this relationship, and our results revealed that two TFs, EGR2 and BHLHE40, were upregulated and five, i.e., TBX2, NR1H3 (LXRα), NR2F1, PPARG (PPARγ), and EPAS1, were downregulated in activated fibroblasts. Notably, PPARγ and LXRα expression was also decreased in an experimental mouse model of silicosis. The mechanism underlying these changes may involve TGF-ß1 secretion from silica-exposed alveolar macrophages, causing PPARγ and LXRα downregulation, which in turn would result in aberrant α-SMA transcription. Our results suggest that LXRα is a potential target for the prevention of silicosis and PF.

Silica particles disorganize the polarization of pulmonary macrophages in mice.

Silicosis is a fatal fibrotic lung disease caused by long-term silica particle exposure, in which pulmonary macrophages play an important role. However, the relationship between macrophage polarization and silicosis remains unclear. We established an experimental silicosis mouse model to investigate macrophage polarization during silicosis development. C57BL/c mice were exposed to silica by intra-tracheal instillation and sacrificed at different time points. Lung tissues and bronchoalveolar lavage fluid were collected for flow cytometry, quantitative reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assays, western blotting, and histology examinations. The polarization of pulmonary macrophages was dysregulated during silicosis development. In the early stage of silicosis, M1 macrophages were induced and played a leading role in eliciting inflammatory; in the late stage, M2 macrophages were induced to promote tissue repair. Levels of several cytokines in lung tissue microenvironment changed with macrophage polarization. Inflammatory cytokines such as tumor necrosis factor-α and interleukin (IL)-1ß and IL-6 were upregulated in the inflammation stage, while the anti-inflammatory cytokine IL-10 was upregulated in the fibrosis stage. Furthermore, we found that STAT (signal transducer and activator of transcription) and IRF (interferon regulatory factor) signaling pathway were involved in the regulation of macrophage polarization in silicosis. In summary, macrophage polarization is closely related to the occurrence and development of silicosis and may be a key point for further elucidating silicosis pathogenesis.