Research on Bearing Surface Scratch Detection Based on Improved YOLOV5.

Bearings are crucial components of machinery and equipment, and it is essential to inspect them thoroughly to ensure a high pass rate. Currently, bearing scratch detection is primarily carried out manually, which cannot meet industrial demands. This study presents research on the detection of bearing surface scratches. An improved YOLOV5 network, named YOLOV5-CDG, is proposed for detecting bearing surface defects using scratch images as targets. The YOLOV5-CDG model is based on the YOLOV5 network model with the addition of a Coordinate Attention (CA) mechanism module, fusion of Deformable Convolutional Networks (DCNs), and a combination with the GhostNet lightweight network. To achieve bearing surface scratch detection, a machine vision-based bearing surface scratch sensor system is established, and a self-made bearing surface scratch dataset is produced as the basis. The scratch detection final Average Precision (AP) value is 97%, which is 3.4% higher than that of YOLOV5. Additionally, the model has an accuracy of 99.46% for detecting defective and qualified products. The average detection time per image is 263.4 ms on the CPU device and 12.2 ms on the GPU device, demonstrating excellent performance in terms of both speed and accuracy. Furthermore, this study analyzes and compares the detection results of various models, demonstrating that the proposed method satisfies the requirements for detecting scratches on bearing surfaces in industrial settings.

Coordinated Transcriptome and Metabolome Analyses of a Barley hvhggt Mutant Reveal a Critical Role of Tocotrienols in Endosperm Starch Accumulation.

Tocotrienols and tocopherols (vitamin E) are potent antioxidants that are synthesized in green plants. Unlike ubiquitous tocopherols, tocotrienols predominantly accumulate in the endosperm of monocot grains, catalyzed by homogentiate geranylgeranyl transferase (HGGT). Previously, we generated a tocotrienol-deficient hvhggt mutant with shrunken barley grains. However, the relationship between tocotrienols and grain development remains unclear. Here, we found that the hvhggt lines displayed hollow endosperms with defective transfer cells and reduced aleurone layers. The carbohydrate and starch contents of the hvhggt endosperm decreased by approximately 20 and 23%, respectively. Weighted gene coexpression network analyses identified a critical gene module containing HvHGGT, which was strongly associated with the hvhggt mutation and enriched with gene functions in starch and sucrose metabolism. Metabolome measurements revealed an elevated soluble sugar content in the hvhggt endosperm, which was significantly associated with the identified gene modules. The hvhggt endosperm had significantly higher NAD(H) and NADP(H) contents and lower levels of ADPGlc (regulated by redox balance) than the wild-type, consistent with the absence of tocotrienols. Interestingly, exogenous α-tocotrienol spraying on developing hvhggt spikes partially rescued starch accumulation and endosperm defects. Our study supports a potential novel function of tocotrienols in grain starch accumulation and endosperm development in monocot crops.

Transcriptional and protein structural characterization of homogentisate phytyltransferase genes in barley, wheat, and oat.

BACKGROUND: Homogentisate phytyltransferase (HPT) is the critical enzyme for the biosynthesis of tocopherols (vitamin E), which are the major lipid-soluble antioxidants and help plants adapt to various stress conditions. HPT is generally strictly conserved in various plant genomes; however, a divergent lineage HPT2 was identified recently in some Triticeae species. The molecular function and transcriptional profiles of HPT2 remain to be characterized. RESULTS: In this study, we performed comprehensive transcriptome data mining of HPT1 and HPT2 in different tissues and stages of barley (Hordeum vulgare), wheat (Triticum aestivum), and oat (Avena sativa), followed by qRT-PCR experiments on HPT1 and HPT2 in different tissues of barley and wheat. We found that the common HPT1 genes (HvHPT1, TaHPT1s, and AsHPT1s) displayed a conserved transcriptional pattern in the three target species and were universally transcribed in various tissues, with a notable preference in leaf. In contrast, HPT2 genes (HvHPT2, TaHPT2, and AsHPT2) were specifically transcribed in spike (developmentally up-regulated) and shoot apex tissues, displaying a divergent tissue-specific pattern. Cis-regulatory elements prediction in the promoter region identified common factors related to light-, plant hormone-, low temperature-, drought- and defense- responses in both HPT1s and HPT2s. We observed the transcriptional up-regulation of HvHPT1 and HvHPT2 under various stress conditions, supporting their conserved function in environmental adaption. We detected a clear, relaxed selection pressure in the HPT2 lineage, consistent with the predicted evolution pattern following gene duplication. Protein structural modelling and substrate docking analyses identified putative catalytic amino acid residues for HvHPT1 and HvHPT2, which are strictly conserved and consistent with their function in vitamin E biosynthesis. CONCLUSIONS: We confirmed the presence of two lineages of HPT in Triticeae and Aveninae, including hexaploid oat, and characterized their transcriptional profiles based on transcriptome and qRT-PCR data. HPT1s were ubiquitously transcribed in various tissues, whilst HPT2s were highly expressed in specific stages and tissue. The active transcription of HPT2s, together with its conserved cis-elements and protein structural features, support HPT2s' role in tocopherol production in Triticeae. This study is the first protein structural analysis on the membrane-bound plant HPTs and provides valuable insights into its catalytic mechanism.

Zearalenone regulates microRNA156 to affect the root development of Tetrastigma hemsleyanum.

Zearalenone (ZEN) is a secondary metabolite from Fusarium species. It is also present in plants and regulates the photochemical reaction in Photosystem II, the stress response and root growth. To investigate the mechanism by which ZEN regulates Tetrastigma hemsleyanum root growth, differentially expressed microRNAs (miRNAs) were identified and verified by high-throughput sequencing and Agrobacterium rhizogenes-mediated transformation of the roots of T. hemsleyanum seedlings treated with and without ZEN. The predicted functions of microRNA156b (miR156b) and microRNA156f (miR156f) were confirmed in transgenic hairy roots. (i) A total of 70 miRNAs showed significantly different expression levels under ZEN treatment, including seven highly conserved miRNAs. (ii) The number of lateral roots and total root length of the transgenic hairy roots overexpressing miR156b and miR156f was significantly higher than the wild-type hairy roots, and thus the overexpression of miR156b and miR156f in T. hemsleyanum promoted lateral root development. (iii) Bioinformatics analysis predicted that the target genes of miR156b and miR156f were SPL9/10. As compared with the wild-type hairy roots, the expression of SPL9 was significantly lower in the hairy roots overexpressing miR156b, and the expression of SPL10 was significantly lower in the hairy roots overexpressing miR156f. Therefore, SPL9 could be the target gene of miR156b, and SPL10 could be the target gene of miR156f. This study shows that ZEN could increase the expression of miR156b and miR156f in T. hemsleyanum roots, which negatively regulated the expression of their putative target genes SPL9 and SPL10, consequently promoting the growth and development of the lateral roots.

Deciphering the potential of a plant growth promoting endophyte Rhizobium sp. WYJ-E13, and functional annotation of the genes involved in the metabolic pathway.

Plant growth-promoting rhizobacteria (PGPR) are well-acknowledged root endophytic bacteria used for plant growth promotion. However, which metabolites produced by PGPR could promote plant growth remains unclear. Additionally, which genes are responsible for plant growth-promoting traits is also not elucidated. Thus, as comprehensive understanding of the mechanism of endophyte in growth promotion is limited, this study aimed to determine the metabolites and genes involved in plant growth-promotion. We isolated an endophytic Rhizobium sp. WYJ-E13 strain from the roots of Curcuma wenyujin Y.H. Chen et C. Ling, a perennial herb and medicinal plant. The tissue culture experiment showed its plant growth-promoting ability. The bacterium colonization in the root was confirmed by scanning electron microscopy and paraffin sectioning. Furthermore, it was noted that the WYJ-E13 strain produced cytokinin, anthranilic acid, and L-phenylalanine by metabolome analysis. Whole-genome analysis of the strain showed that it consists of a circular chromosome of 4,350,227 bp with an overall GC content of 60.34%, of a 2,149,667 bp plasmid1 with 59.86% GC, and of a 406,180 bp plasmid2 with 58.05% GC. Genome annotation identified 4,349 putative protein-coding genes, 51 tRNAs, and 9 rRNAs. The CDSs number allocated to the Kyoto Encyclopedia of Genes and Genomes, Gene Ontology, and Clusters of Orthologous Genes databases were 2027, 3,175 and 3,849, respectively. Comparative genome analysis displayed that Rhizobium sp. WYJ-E13 possesses the collinear region among three species: Rhizobium acidisoli FH23, Rhizobium gallicum R602 and Rhizobium phaseoli R650. We recognized a total set of genes that are possibly related to plant growth promotion, including genes involved in nitrogen metabolism (nifU, gltA, gltB, gltD, glnA, glnD), hormone production (trp ABCDEFS), sulfur metabolism (cysD, cysE, cysK, cysN), phosphate metabolism (pstA, pstC, phoB, phoH, phoU), and root colonization. Collectively, these findings revealed the roles of WYJ-E13 strain in plant growth-promotion. To the best of our knowledge, this was the first study using whole-genome sequencing for Rhizobium sp. WYJ-E13 associated with C. wenyujin. WYJ-E13 strain has a high potential to be used as Curcuma biofertilizer for sustainable agriculture.

Role of female-predominant MYB39-bHLH13 complex in sexually dimorphic accumulation of taxol in Taxus media.

Taxus trees are major natural sources for the extraction of taxol, an anti-cancer agent used worldwide. Taxus media is a dioecious woody tree with high taxol yield. However, the sexually dimorphic accumulation of taxoids in T. media is largely unknown. Our study revealed high accumulation of taxoids in female T. media trees using a UPLC-MS/MS method. Thereafter, many differential metabolites and genes between female and male T. media trees were identified using metabolomic and transcriptomic analyses, respectively. Most of the taxol-related genes were predominantly expressed in female trees. A female-specific R2R3-MYB transcription factor gene, TmMYB39, was identified. Furthermore, bimolecular fluorescence complementation and yeast two-hybrid assays suggested the potential interaction between TmMYB39 and TmbHLH13. Several taxol biosynthesis-related promoter sequences were isolated and used for the screening of MYB recognition elements. The electrophoretic mobility shift assay indicated that TmMYB39 could bind to the promoters of the GGPPS, T10OH, T13OH, and TBT genes. Interaction between TmMYB39 and TmbHLH13 transactivated the expression of the GGPPS and T10OH genes. TmMYB39 might function in the transcriptional regulation of taxol biosynthesis through an MYB-bHLH module. Our results give a potential explanation for the sexually dimorphic biosynthesis of taxol in T. media.

Environmental and Genetic Factors Involved in Plant Protection-Associated Secondary Metabolite Biosynthesis Pathways.

Plant specialized metabolites (PSMs) play essential roles in the adaptation to harsh environments and function in plant defense responses. PSMs act as key components of defense-related signaling pathways and trigger the extensive expression of defense-related genes. In addition, PSMs serve as antioxidants, participating in the scavenging of rapidly rising reactive oxygen species, and as chelators, participating in the chelation of toxins under stress conditions. PSMs include nitrogen-containing chemical compounds, terpenoids/isoprenoids, and phenolics. Each category of secondary metabolites has a specific biosynthetic pathway, including precursors, intermediates, and end products. The basic biosynthetic pathways of representative PSMs are summarized, providing potential target enzymes of stress-mediated regulation and responses. Multiple metabolic pathways share the same origin, and the common enzymes are frequently to be the targets of metabolic regulation. Most biosynthetic pathways are controlled by different environmental and genetic factors. Here, we summarized the effects of environmental factors, including abiotic and biotic stresses, on PSM biosynthesis in various plants. We also discuss the positive and negative transcription factors involved in various PSM biosynthetic pathways. The potential target genes of the stress-related transcription factors were also summarized. We further found that the downstream targets of these Transcription factors (TFs) are frequently enriched in the synthesis pathway of precursors, suggesting an effective role of precursors in enhancing of terminal products. The present review provides valuable insights regarding screening targets and regulators involved in PSM-mediated plant protection in non-model plants.

Ultraviolet-B Irradiation Increases Antioxidant Capacity of Pakchoi (Brassica rapa L.) by Inducing Flavonoid Biosynthesis.

As an important abiotic stress factor, ultraviolet-B (UV-B) light can stimulate the accumulation of antioxidants in plants. In this study, the possibility of enhancing antioxidant capacity in pakchoi (Brassica rapa L.) by UV-B supplementation was assessed. Irradiation with 4 µmol·m-2·s-1 UV-B for 4 h or 2 µmol·m-2·s-1 UV-B for 24 h significantly increased the 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and total reductive capacity, as a result of inducing a greater accumulation of total polyphenols and flavonoids without affecting the plant biomass. A high performance liquid chromatography (HPLC) analysis showed that the concentrations of many flavonoids significantly increased in response to UV-B treatment. The activities of three enzymes involved in the early steps of flavonoid biosynthesis, namely phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate: coenzyme A (CoA) ligase (4CL), were significantly increased after the corresponding UV-B treatment. Compared with the control, the expression levels of several flavonoid biosynthesis genes (namely BrPAL, BrC4H, Br4CL, BrCHS, BrF3H, BrF3'H, BrFLS, BrDFR, BrANS, and BrLDOX) were also significantly up-regulated in the UV-B treatment group. The results suggest that appropriate preharvest UV-B supplementation could improve the nutritional quality of greenhouse-grown pakchoi by promoting the accumulation of antioxidants.

Identification of the function and regulatory network of circ_009773 in DNA damage induced by nanoparticles of neodymium oxide.

The health hazards of nanoparticles of neodymium oxide (NPs-Nd2O3) have aroused public concern in recent years. Exposure to NPs-Nd2O3 can change the level of reactive oxygen species (ROS) that cause DNA damage and alter whole transcriptome expression profiles for micro (mi)RNA, circular (circ)RNA, long noncoding (lnc)RNA, and mRNA. However, there have been no reports to our knowledge about the role of circRNAs in DNA damage caused by NPs-Nd2O3. In our study, we analyzed the circRNA expression profile of human bronchial epithelial cells(16HBE)exposed to 40 µg/ml NPs-Nd2O3. Our results indicated that exposure produced 1025 up-regulated and 890 down-regulated circRNAs. Real-time quantitative polymerase chain reaction (qRT-PCR) was applied to verify some of the significantly changed circRNAs and demonstrated that circ_009773 was apparently down-regulated. Through exploration of its host gene function, we found that circ_009773 may be related to DNA damage. Functional experiments found that circ_009773 regulated NPs-Nd2O3-induced DNA damage in 16HBE cells. A circ_009773-associated competing endogenous (ce)RNA network was constructed based on one differentially expressed (DE) circRNA, 74 DE miRNAs and 208 DE mRNAs. Module analysis identified hub genes related to DNA damage and repair and a protein-protein interaction (PPI) network was created.

GrTCP11, a Cotton TCP Transcription Factor, Inhibits Root Hair Elongation by Down-Regulating Jasmonic Acid Pathway in Arabidopsis thaliana.

TCP transcription factors play important roles in diverse aspects of plant development as transcriptional activators or repressors. However, the functional mechanisms of TCPs are not well understood, especially in cotton fibers. Here, we identified a total of 37 non-redundant TCP proteins from the diploid cotton (Gossypium raimondii), which showed great diversity in the expression profile. GrTCP11, an ortholog of AtTCP11, was preferentially expressed in cotton anthers and during fiber initiation and secondary cell wall synthesis stages. Overexpression of GrTCP11 in Arabidopsis thaliana reduced root hair length and delayed flowering. It was found that GrTCP11 negatively regulated genes involved in jasmonic acid (JA) biosynthesis and response, such as AtLOX4, AtAOS, AtAOC1, AtAOC3, AtJAZ1, AtJAZ2, AtMYC2, and AtERF1, which resulted in a decrease in JA concentration in the overexpressed transgenic lines. As with the JA-deficient mutant dde2-2, the transgenic line 4-1 was insensitive to 50 µM methyl jasmonate, compared with the wild-type plants. The results suggest that GrTCP11 may be an important transcription factor for cotton fiber development, by negatively regulating JA biosynthesis and response.

Cloning, Expression, and Tobacco Overexpression Analyses of a PISTILLATA/GLOBOSA-like (OfGLO1) Gene from Osmanthus fragrans.

GLOBOSA (GLO), a B-class MADS-box gene, is involved in floral organ determination but has rarely been studied in Osmanthus fragrans, which is a very popular ornamental tree species in China. Here, the full-length cDNA of a homologous GLO1 gene (named OfGLO1) was cloned from a flower bud of O. fragrans using the RACE technique. The OfGLO1 has a 645 bp open reading frame, encoding 214 amino acids. Similar to other PI/GLO proteins, OfGLO1 has two conserved domains, MADS MEF2-like and K-box, and a 16-amino-acid PI motif in the C terminal region. Our phylogeny analysis classified OfGLO1 as a PI-type member of the B-class MADS-box gene family. The qRT-PCR assay showed that the expression of OfGLO1 in O. fragrans was continuously upregulated from the tight bud stage to the full flowering stage but barely expressed in the pistils, sepals, and non-floral organs, such as root, leaf, and stem. The genetic effect of OfGLO1 was assayed by ectopic expression in tobacco plants. Compared with the wild-type, OfGLO1 transformants showed reduced plant size, earlier flowering, shorter stamens, and lower seed setting rates. Furthermore, some stamens were changed into petal-like structures. These findings indicate that OfGLO1 plays an important role in the regulation of flower development. This study improved our understanding of class B gene function in woody plants.

UV RESISTANCE LOCUS 8 From Chrysanthemum morifolium Ramat (CmUVR8) Plays Important Roles in UV-B Signal Transduction and UV-B-Induced Accumulation of Flavonoids.

UV Resistance Locus 8 (UVR8), an ultraviolet-B (UV-B; 280-315 nm) photoreceptor, participates in the regulation of various plant growth and developmental processes. UV-B radiation is an important factor enhancing the production of active components in medicinal plants. To-date, however, studies on UV-B photoreceptors have largely focused on Arabidopsis, and the functions of UVR8 in medicinal plants are still largely unknown. In the present study, a homolog of Arabidopsis UVR8, CmUVR8, was isolated from Chrysanthemum morifolium Ramat, and its structure and function were analyzed in detail. Protein sequence analysis showed that CmUVR8 contained nine conserved regulators of chromosome condensation 1 repeats, seven conserved bladed propellers, one C27 region, three "GWRHT" motifs and several crucial amino acid residues (such as 14 Trps and 2 Args), similar to AtUVR8. 3-D structural analysis of CmUVR8 indicated that its structure was similar to AtUVR8. Heterologous expression of CmUVR8 could rescued the deficient phenotype of uvr8-6, a mutant of UVR8 in Arabidopsis, indicating the role of CmUVR8 in the regulation of hypocotyl elongation and HY5 gene expression under UV-B irradiation. Moreover, CmUVR8 regulates UV-B-induced expression of four flavonoids biosynthesis-related genes and the UV-B-induced accumulation of flavonoids. Furthermore, the interaction between CmUVR8 and CmCOP1 were confirmed using a yeast two-hybrid assay. These results indicated that CmUVR8 plays important roles in UV-B signal transduction and the UV-B-induced accumulation of flavonoids, as a counterpart of AtUVR8.

Identification and Expression Profiling of the Auxin Response Factors in Dendrobium officinale under Abiotic Stresses.

Auxin response factor (ARF) proteins play roles in plant responses to diverse environmental stresses by binding specifically to the auxin response element in the promoters of target genes. Using our latest public Dendrobium transcriptomes, a comprehensive characterization and analysis of 14 DnARF genes were performed. Three selected DnARFs, including DnARF1, DnARF4, and DnARF6, were confirmed to be nuclear proteins according to their transient expression in epidermal cells of Nicotiana benthamiana leaves. Furthermore, the transcription activation abilities of DnARF1, DnARF4, and DnARF6 were tested in a yeast system. Our data showed that DnARF6 is a transcriptional activator in Dendrobium officinale. To uncover the basic information of DnARF gene responses to abiotic stresses, we analyzed their expression patterns under various hormones and abiotic treatments. Based on our data, several hormones and significant stress responsive DnARF genes have been identified. Since auxin and ARF genes have been identified in many plant species, our data is imperative to reveal the function of ARF mediated auxin signaling in the adaptation to the challenging Dendrobium environment.

Overexpression of a miR393-resistant form of transport inhibitor response protein 1 (mTIR1) enhances salt tolerance by increased osmoregulation and Na+ exclusion in Arabidopsis thaliana.

Soil salinity is a common environmental stress factor that limits agricultural production worldwide. Plants have evolved different strategies to achieve salt tolerance. miR393 has been identified as closely related to biotic and abiotic stresses, and targets F-box genes that encode auxin receptors. The miR393-TIR1/AFB2/AFB3 regulatory module was discovered to have multiple functions that manipulate the auxin response. This study focused on miR393 and one of its targets, TIR1, and found that they played potential roles in response to salt stress. Our results showed that overexpression of a miR393-resistant TIR1 gene (mTIR1) in Arabidopsis clearly enhanced salt stress tolerance, which led to a higher germination rate, less water loss, reduced inhibition of root elongation, delayed senescence, decreased death rate and stabilized Chl content. These plants accumulated more proline and anthocyanin, and displayed enhanced osmotic stress tolerance. The expression of some salt stress-related genes was altered, and sodium content can be reduced in these plants under salt stress. We proposed that highly increased auxin signaling by overexpression of mTIR1 may trigger auxin-mediated downstream pathways to enhance plant salt stress resistance by osmoregulation and increased Na(+) exclusion.

miR396a-Mediated basic helix-loop-helix transcription factor bHLH74 repression acts as a regulator for root growth in Arabidopsis seedlings.

miR396 targets seven GROWTH-REGULATING FACTOR (GRF) genes and the BASIC HELIX-LOOP-HELIX (bHLH) TRANSCRIPTION FACTOR 74 gene (bHLH74) in Arabidopsis. Previous research revealed that the miR396 target module regulates cell proliferation and plays a critical role in leaf development. However, no additional biological functions of miR396 have been investigated in detail. In this study, T-DNA insertion mutants and transgenic plants with altered levels of miR396 or its target genes were used to characterize the regulatory role of miR396 in root development. We found that AtMIR396a was the predominant source for miR396 accumulation in the roots of seedlings, and that the mir396a-1 mutant had longer roots than wild-type seedlings. Overexpression of AtMIR396a decreased the transcript levels of target genes such as GRF genes and bHLH74, and resulted in a shorter root phenotype. Furthermore, the bhlh74-1 mutant had shorter roots, whereas overexpression of an miR396-resistant form of bHLH74 (mbHLH74) had an enhanced root growth phenotype. Moreover, MIR396a regulated root growth by affecting the elongation zone. Taken together, these data indicate that miR396a-mediated bHLH74 repression helps regulate root growth in Arabidopsis seedlings.

Virus-induced gene silencing of PEAM4 affects floral morphology by altering the expression pattern of PsSOC1a and PsPVP in pea.

pea-MADS4 (PEAM4) regulates floral morphology in Pisum sativum L., however, its molecular mechanisms still remain unclear. Virus-induced gene silencing (VIGS) is a recently developed reverse genetic approach that facilities an easier and more rapid study of gene functions. In this study, the PEAM4 gene was effectively silenced by VIGS using a pea early browning virus (PEBV) in wild type pea JI992. The infected plants showed abnormal phenotypes, as the floral organs, especially the sepals and petals changed in both size and shape, which made the corolla less closed. The petals changed in morphology and internal symmetry with, the stamens reduced and carpel dehisced. Larger sepals and longer tendrils with small cauline leaves appeared, with some sepals turning into bracts, and secondary inflorescences with fused floral organs were formed, indicating a flower-to-inflorescence change. The infected plants also displayed a delayed and prolonged flowering time. The PEAM4-VIGS plants with altered floral morphology were similar to the pim (proliferating inflorescence meristem) mutant and also mimicked the phenotypes of ap1 mutants in Arabidopsis. The expression pattern of the homologous genes PsSOC1a and PsSVP, which were involved in flowering time and florescence morphological control downstream of PEAM4, were analyzed by real-time RT-PCR and mRNA in situ hybridization. PsSOC1a and PsSVP were ectopically expressed and enhanced in the floral meristems from PEAM4-silenced plants. Our data suggests that PEAM4 may have a similar molecular mechanism as AtAP1, which inhibits the expression of PsSOC1a and PsSVP in the floral meristem from the early stages of flower development. As such, in this way PEAM4 plays a crucial role in maintaining floral organ identity and flower development in pea.

A chloroplast envelope membrane protein containing a putative LrgB domain related to the control of bacterial death and lysis is required for chloroplast development in Arabidopsis thaliana.

• A protein encoded by At1g32080 was consistently identified in proteomic studies of Arabidopsis chloroplast envelope membranes, but its function remained unclear. The protein, designated AtLrgB, may have evolved from a gene fusion of lrgA and lrgB. In bacteria, two homologous operons, lrgAB and cidAB, participate in an emerging mechanism to control cell death and lysis. • We aim to characterize AtLrgB using reverse genetics and cell biological and biochemical analysis. • AtLrgB is expressed in leaves, but not in roots. T-DNA insertion mutation of AtLrgB produced plants with interveinal chlorotic and premature necrotic leaves. Overexpression of full-length AtLrgB (or its LrgA and LrgB domains, separately), under the control of CaMV 35S promoter, produced plants exhibiting veinal chlorosis and delayed greening. At the end of light period, the T-DNA mutant had high starch and low sucrose contents in leaves, while the 35S:AtLrgB plants had low starch and high sucrose contents. Metabolite profiling revealed that AtLrgB appeared not to directly transport triose phosphate or hexose phosphates. In yeast cells, AtLrgB could augment nystatin-induced membrane permeability. • Our work indicates that AtLrgB is a new player in chloroplast development, carbon partitioning and leaf senescence, although its molecular mechanism remains to be established.

Regulation of auxin response by miR393-targeted transport inhibitor response protein 1 is involved in normal development in Arabidopsis.

miR393, which is encoded by MIR393a and MIR393b in Arabidopsis, post-transcriptionally regulates mRNAs for the F-box auxin receptors TIR1 (Transport Inhibitor Response Protein 1), AFB1 (Auxin Signaling F-box Protein 1), AFB2 and AFB3. However, biological functions of the miR393-TIR1/AFBs module in auxin response and plant development is not fully understood. In the study herein, we demonstrate that miR393 accumulated in response to exogenous IAA treatment, and its induction was due to enhanced MIR393b transcription but not MIR393a. Overexpression of a miR393-resistant form of TIR1 (mTIR1) enhanced auxin sensitivity and led to pleiotropic effects on plant development including inhibition of primary root growth, overproduction of lateral roots, altered leave phenotype and delayed flowering. Furthermore, miR393 level was increased in 35S:mTIR1 plant, suggesting that TIR1 promoted the expression of miR393 by a feedback loop. The interaction between miR393 and its target indicates a fine adjustment to the roles of the miR393-TIR1 module, which is required for auxin responses in plant development.