Root tips can sense moisture gradients and grow into environments with higher water potential. This process is called root hydrotropism. Here, we report three closely related receptor-like kinases (RLKs) that play critical roles in root hydrotropism: ALTERED ROOT HYDROTROPIC RESPONSE 1 ( ARH1 ), FEI1 , and FEI2 . Overexpression of these RLKs strongly reduce root hydrotropism, but corresponding loss-of-function mutants exhibit an increased hydrotropic response in their roots. All these RLKs show polar localization at the plasma membrane regions in root tips. The biosynthesis of the cell wall, cutin, and wax (CCW) is significantly impaired in root tips of arh1-2 fei1-C fei2-C . A series of known CCW mutants also exhibit increased root hydrotropism and reduced osmotic tolerance, similar to the characteristics of the triple mutant. Our results demonstrat that the integrity of the cell wall, cutin, and root cap wax mediate a trade-off between root hydrotropism and osmotic tolerance.

Tropisms are growth-based plant directional movements, allowing plants to respond to their living environments. Plant roots have developed various tropic responses, including gravitropism, hydrotropism, chemotropism, and halotropism, in response to the gravity, moisture gradient, nutrient gradient, and salinity gradient, respectively. Revealed mechanisms of several tropic responses suggested that plant hormone gradient and cell division activity play key roles in determining these responses. Approaches to measure cell division and hormone gradients, however, have rarely been applied in root tropic analyses. Here, we describe a number of methods to quantify cell division and hormone gradients during root tropic analysis. These approaches are mainly based on our previous researches on root hydrotropism.

Rooting is a key innovation during plant terrestrialization. RGFs/GLVs/CLELs are a family of secreted peptides, playing key roles in root stem cell niche maintenance and pattern formation. The origin of this peptide family is not well characterized. RGFs and their receptor genes, RGIs, were investigated comprehensively using phylogenetic and genetic analyses. We identified 203 RGF genes from 24 plant species, representing a variety of land plant lineages. We found that the RGF genes originate from land plants and expand via multiple duplication events. The lineage-specific RGF duplicates are retained due to their regulatory divergence, while a majority of RGFs experienced strong purifying selection in most land plants. Functional analysis indicated that RGFs and their receptor genes, RGIs, isolated from liverwort, tomato, and maize possess similar biological functions with their counterparts from Arabidopsis in root development. RGFs and RGIs are likely coevolved in land plants. Our studies shed light on the origin and functional conservation of this important peptide family in plant root development.

Summary Receptor‐like protein kinases (RLKs) play key roles in regulating plant growth, development and stress adaptations. There are at least 610 RLKs (including receptor‐like cytoplasmic kinases) in Arabidopsis. The functions of the majority of RLKs have not yet been determined. We previously generated promoter:: GUS transgenic plants for all leucine‐rich repeat ( LRR )‐ RLKs in Arabidopsis and analyzed their expression patterns during various developmental stages. We found the expression of two LRR‐RLKs , MUSTACHES ( MUS ) and MUSTACHES‐LIKE ( MUL ), are overlapped in lateral root primordia. Independent mutants, mus‐3 mul‐1 and mus‐4 mul‐2 , show a significantly decreased emerged lateral root phenotype. Our analyses indicate that the defects of the double mutant occur mainly at stage I of lateral root development. Exogenous application of auxin can dramatically enhance the transcription of MUS , which is largely dependent on AUXIN RESPONSE FACTOR 7 (ARF7) and ARF19. MUS and MUL are inactive kinases in vitro but are phosphorylated in planta , possibly by an unknown kinase. The kinase activity of MUS is dispensable for its function in lateral root development. Many cell wall related genes are down regulated in mus‐3 mul‐1 . In conclusion, we identified MUS and MUL, two kinase‐inactive RLKs, in controlling the early development of lateral root primordia likely via regulating cell wall synthesis and remodeling.

Root growth is maintained by the continuous division of cells in the apical meristem. ROOT MERISTEM GROWTH FACTOR 1 (RGF1) is a critical peptide hormone regulating root stem cell niche maintenance. Previous studies discovered that five closely related leucine-rich repeat receptor-like protein kinases (LRR-RLKs), named RGF1 INSENSITIVES (RGIs) or RGF1 RECEPTORS (RGFRs), are able to perceive the RGF1 signal and redundantly control root stem cell niche maintenance. RGF1 regulates root meristem activity mainly via two downstream transcription factors, PLETHORA 1 (PLT1) and PLT2. Regulatory proteins connecting cell surface RGF1-RGI1 and nuclear PLTs, however, were not identified. Here, we report that the mitogen-activated protein (MAP) kinase kinase 4 (MKK4) and MAP kinase 3 (MPK3) were co-immunoprecipitated with RGI1-FLAG after Arabidopsis seedlings were treated with RGF1. Genetic and biochemical assays confirmed that MKK4 and MKK5, and their downstream targets MPK3 and MPK6, are essential RGI-dependent regulators of root meristem development. In addition, we found that the MKK4/MKK5-MPK3/MPK6 module functions downstream of YDA, a MAPKKK. Our results demonstrate that RGF1-RGI1 regulate the expression of PLT1/PLT2 via a YDA-MKK4/MKK5-MPK3/MPK6 signaling cascade.

The phenomenon of plant root tips sensing moisture gradient in soil and growing towards higher water potential is designated as root hydrotropism, which is critical for plants to survive when water is a limited factor. Molecular mechanisms regulating such a fundamental process, however, are largely unknown. Here we report our identification that cytokinins are key signaling molecules directing root growth orientation in a hydrostimulation (moisture gradient) condition. Lower water potential side of the root tip shows more cytokinin response relative to the higher water potential side. Consequently, two cytokinin downstream type-A response regulators, ARR16 and ARR17, were found to be up-regulated at the lower water potential side, causing increased cell division in the meristem zone, which allows the root to bend towards higher water potential side. Genetic analyses indicated that various cytokinin biosynthesis and signaling mutants, including the arr16 arr17 double mutant, are significantly less responsive to hydrostimulation. Consistently, treatments with chemical inhibitors interfering with either cytokinin biosynthesis or cell division completely abolished root hydrotropic response. Asymmetrically induced expression of ARR16 or ARR17 effectively led to root bending in both wild-type and miz1, a previously known hydrotropism-defective mutant. These data demonstrate that asymmetric cytokinin distribution is a primary determinant governing root hydrotropism.

Plant root tips can sense the moisture gradient in soil and grow toward the higher water potential region.This unique response is called the hydrotropic response or hydrotropism.Hydrotropism plays a key role for plants to efficiently obtain water from soil.The root hydrotropic response has become one of the hot topics in plant biology.However,the detailed molecular mechanisms controlling the root hydrotropic response are poorly understood.Previous studies demonstrated that MIZ1 and GNOM can positively regulate the hydrotropic response.Several phytohormones,light,ROS and Ca2+ were also thought to mediate the root hydrotropic response,but their detailed molecular mechanisms are not yet elucidated.This review highlights the research history and factors of hydrotropic response and identification and characterization of key regulators of hydrotropic response,to give a more comprehensive understanding of research progress in the plant hydrotropic response.We provide perspectives on possible future research directions.

Phytohormones,as signaling molecules,play critical roles in regulating cell-to-cell and cell-to-environment communications.The mechanisms plant cells use to perceive phytohormones remain hot research topics in plant biology.Previous studies indicated that most plant hormones are perceived by non-covalent physical interactions with their corresponding receptors.After signaling pathways are initiated,the ligands usually dissociate with their binding receptors,which can interact with other receptor molecules or go through a degradation pathway.Therefore,ligand-receptor interaction is distinct from substrate-enzyme association.Recently,Xie and colleagues resolved a 3D structure of a strigolactone-induced AtD14-D3-ASK1 receptor complex.Strigolactones could be cleaved into a covalent-linked intermediate molecule in the reaction center of AtD14,the receptor of strigolactones.Further analyses revealed detailed molecular mechanisms of strigolactone-induced ligand-receptor complex formation and subsequent signaling initiation.Such a mechanism has never been reported in plants.These results provide significant insights into our better understanding of cellular signaling in plants.

Biohydrogen was produced from apple residue through solid-state anaerobic fermentation. Influences of pretreatment conditions of natural sludge and apple residue and ferment conditions on the biehydrogen production from apple residue were studied. Results indicated that the maximum hydrogen yield of 16.47mL/gTS was obtained under the condition of pill 1 pretreating natural sludge for 1.5h,apple residue was soaked by 1% NaOH for 2h after been comminuted at 2000μm granularity,apple residue：bran：water at 4：1：25. It was showed that biohydrogen by solid-state anaerebic fermentation had great poteniial for development.

Four different enhancing methods including mechanical stirring (MS), flat plate ultrasonic irradiation (FPUI), fiat plate ultrasonic irradiation with mechanical stirring (UIMS) and probe ultrasonic irradiation (PUI) were studied to select a better one that need less catalyst, energy consumption and time to reach equilibrium for preparing biodiesel through transesterification of sunflower oil. The molar ratio of methanol to oil (3:1, 4:1, 5:1, 6:1, 7:1, 10:1 and 15:1), the catalyst concentration (0.5 wt.%, 1.0 wt.%, 1.5 wt.% and 2.0 wt.% of the weight of oil), the equilibrium time and energy consumption were studied. The PUI and UIMS methods reached the highest biodiesel conversion when methanol to oil ratio was 5:1 while that for MS was 6:1 and for FPUI was7:1. The suitable catalyst concentration for the reaction was 1.5 wt.%. At the same condition, the PUI and UIMS reached maximum biodiesel conversion about 25 min and that for MS and FPUI was about 50 min. The energy consumption of PUI and UIMS had no significant difference and were 0.19 kW h, 0.18 kW h, respectively. Results showed that under the same condition, UIMS and PUI used less catalyst, less methanol, shorter time and less energy consumption than MS and FPUI with the same biodiesel conversion. (C) 2011 Elsevier Ltd. All rights reserved.

Extraction and purification technology of lipid-soluble anti-tumor active components from fig residues were studied. Thirteen crystals were got after column chromatography, spectrometric study and structural analysis. The anti-tumor activity of these 13 crystals was investigated on blood tumor cell line(U937), lung tumor cell line(95D)and stomach tumor cell line(AGS)in vitro. The Number 6 crystal was identified as β-sitosterol and validated as anti-tumor component for its fifty percent inhibition content (IC50)lower than 10mg/L. The optimum lipid-soluble anti-tumor components extraction condition are as follows, using petroleum ether(boiling point from 60 to 90℃) as solvent and the fig residues granularity 750μm, extracting temperature 85℃, extracting time 130min, the ratio of solid to solvent 1∶11(g∶mL), extracting twice. As a result the anti-tumor substance extraction yield is 23.1g/kg. The anti-tumor component was identified as β-sitosterol after column chromatography, spectrometric study and structural analysis.

The vinegar residues are the byproduct of vinegar brewing and have the characteristics of high acidity and slow rotting,which is a big problem of the urban environmental sanitation management.This paper introduces the research of vinegar residue utilization in feed,mushroom planting material,medicine and bio-energy.The prospect was also discussed.