In this review, we summarize the different biosynthesis-related pathways that contribute to the regulation of endogenous auxin in plants. We demonstrate that all known genes involved in auxin biosynthesis also have a role in root formation, from the initiation of a root meristem during embryogenesis to the generation of a functional root system with a primary root, secondary lateral root branches and adventitious roots. Furthermore, the versatile adaptation of root development in response to environmental challenges is mediated by both local and distant control of auxin biosynthesis. In conclusion, auxin homeostasis mediated by spatial and temporal regulation of auxin biosynthesis plays a central role in determining root architecture.

Acacia auriculiformis Cunn. Ex. Benth is a multipurpose wattle tree with diverse environmental and ecological significance. However, seeds dormancy and low germination percentage are problems for its use in agro-forestry practices. Investigations were carried out on the effect of pre-treatment on the germination and early seedlings growth of A. auriculiformis. Germination were observed in seeds pretreated with sulphuric acid at 7days after sowing (DAS) while seeds under the nitric acid and control treatment germinated at 8 and 9 DAS respectively. Results, shown that pre-sowing treatments have positive influence on seed germination; seeds treated with Conc. H 2 SO 4 for 5 to 10 min had the highest percentage germination of 92-96% compared with 42% for the control treatment. The effect of different pre-treatment test, their interaction and time of exposure significantly (P < 0.05) influenced seedlings growth parameters. The highest mean shoot length and stem diameter values of 5.92 cm and 0.29 mm respectively were recorded among seedlings that originated from seeds pre-treated with sulphuric acid for 5 and 10 min. Hence, dormancy in A. auriculiformis seeds can be removed by pre-treatment with sulphuric acid (5 and10 min) with enhanced percentage germination and growth performances.

No abstract

Protein activity, abundance, and stability can be regulated by posttranslational modification including ubiquitination. Ubiquitination is conserved among eukaryotes and plays a central role in modulating cellular function and yet we lack comprehensive catalogs of proteins that are modified by ubiquitin in plants. In this study, we describe an antibody-based approach to enrich peptides containing the di-glycine (diGly) remnant of ubiquitin and coupled that with isobaric labeling to enable quantification, from up to 16-multiplexed samples, for plant tissues. Collectively, we identified 7,130 diGly-modified lysine residues sites arising from 3,178 proteins in Arabidopsis primary roots. These data include ubiquitin proteasome dependent ubiquitination events as well as ubiquitination events associated with auxin treatment. Gene Ontology analysis indicated that ubiquitinated proteins are associated with numerous biological processes including hormone signaling, plant defense, protein homeostasis, and root morphogenesis. We determined the ubiquitinated lysine residues that directly regulate the stability of the transcription factors CRYPTOCHROME-INTERACTING BASIC-HELIX-LOOP-HELIX 1 (CIB1), CIB1 LIKE PROTEIN 2 (CIL2), and SENSITIVE TO PROTON RHIZOTOXICITY (STOP1) using site directed mutagenesis and in vivo degradation assays. These comprehensive site-level ubiquitinome profiles provide a wealth of data for future studies related to modulation of biological processes mediated by this posttranslational modification in plants.

Myosins are evolutionarily conserved motor proteins that interact with actin filaments to regulate organelle transport, cytoplasmic streaming and cell growth. Plant-specific Class XI myosin proteins direct cell division and root organogenesis. However, the roles of plant-specific Class VIII myosin proteins in plant growth and development are less understood. Here, we investigated the function of an auxin-regulated Class VIII myosin, Arabidopsis thaliana Myosin 1 (ATM1), using genetics, transcriptomics, and live cell microscopy. ATM1 is associated with the plasma membrane and plasmodesmata within the root apical meristem (RAM). Loss of ATM1 function results in decreased RAM size and reduced cell proliferation in a sugar-dependent manner. Auxin signaling and transcriptional responses were dampened in atm1-1 roots. Complementation of atm1-1 with a tagged ATM1 driven under the native ATM1 promoter restored root growth and cell cycle progression. Genetic analyses of atm1-1 seedlings with gin2 (hexokinase) and target of rapamycin complex 1 (TORC1) overexpression lines indicate that ATM1 is downstream of TOR. Collectively, these results provide novel evidence that ATM1 functions to influence cell proliferation in primary roots in response to auxin and sugar cues.

Myosins are evolutionarily conserved motor proteins that interact with actin filaments to regulate organelle transport, cytoplasmic streaming and cell growth. Plant-specific Class XI myosin proteins direct cell division and root organogenesis. However, the roles of plant-specific Class VIII myosin proteins in plant growth and development are less understood. Here, we investigated the function of an auxin-regulated Class VIII myosin, Arabidopsis thaliana Myosin 1 (ATM1), using genetics, transcriptomics, and live cell microscopy. ATM1 is expressed in the primary root, adventitious roots and throughout lateral root development. ATM1 is a plasma membrane localized protein that is enriched in actively dividing cells in the root apical meristem (RAM). Loss of ATM1 function results in impaired primary root growth due to decreased RAM size and reduced cell proliferation in a sugar-dependent manner. In ATM1 loss-of-function roots, columella reporter gene expression is diminished, and fewer columella stem cell divisions occur. In addition, atm1-1 roots displayed reduced auxin responses and auxin marker gene expression. Complementation of atm1-1 with a tagged ATM1 driven under the native ATM1 promoter restored root growth and cell cycle progression in the root meristem. Collectively, these results provide novel evidence that ATM1 functions to influence cell proliferation and columella differentiation in primary roots in response to auxin and sugar cues.

No abstract

Veterinary antibiotics are commonly used in poultry farming for preventing diseases and promoting growth. As a result of their incomplete metabolism in poultry birds, veterinary antibiotics are usually excreted and are frequently detected in poultry manures. Veterinary antibiotics in poultry manure applied onto soil may pose serious ecological effect to the terrestrial and aquatic environment. In the present work, the occurrence of three veterinary antibiotics (sulfamethoxazole, sulfadimidine and trimethoprim), categorized as veterinary antimicrobial agents of critical importance, was investigated in poultry manure from two poultry farms in Nigeria. The potential ecotoxicological risk of target veterinary antibiotics in poultry manure-amended soil was also assessed. A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction was adopted for the extraction of target veterinary antibiotics and instrumental analysis was achieved by high performance liquid chromatography. Sulfamethoxazole, sulfadimidine and trimethoprim were quantified in poultry manures from the poultry farms up to 12.7 μg g^-1, 16.1 μg g^-1 and 33.8 μg g^-1, respectively. Sulfamethoxazole and trimethoprim in poultry manure-amended soil presented low risk to Eisenia fetida (earthworm). The ecological effect of sulfamethoxazole for the root length of rice was high in Farm B and medium in Farm A. Sulfamethoxazole presented high risk to aquatic organisms while sulfadimidine and trimethoprim posed medium risk and low risk, respectively to aquatic organisms. The results indicated that residual veterinary antibiotics in poultry manures could have adverse effects on crops after application to agricultural soil. There is a need for effective enlightenment programs for poultry farmers in Nigeria to bring about awareness on the environmental and toxicological impact of the excessive and uncontrolled use of veterinary antibiotics in poultry farming and the adverse ecological implications of poultry manure application on farmlands.