Mutation of CESA1 phosphorylation site influences pectin synthesis and methylesterification with a role in seed development.

Cell wall biogenesis is required for the production of seeds of higher plants. However, little is known about regulatory mechanisms underlying cell wall biogenesis during seed formation. Here we show a role for the phosphorylation of Arabidopsis cellulose synthase 1 (AtCESA1) in modulating pectin synthesis and methylesterification in seed coat mucilage. A phosphor-null mutant of AtCESA1 on T166 (AtCESA1T166A) was constructed and introduced into a null mutant of AtCESA1 (Atcesa1-1). The resulting transgenic lines showed a slight but significant decrease in cellulose contents in mature seeds. Defects in cellulosic ray architecture along with reduced levels of non-adherent and adherent mucilage were observed on the seeds of the AtCESA1T166A mutant. Reduced mucilage pectin synthesis was also reflected by a decrease in the level of uronic acid. Meanwhile, an increase in the degree of pectin methylesterification was also observed in the seed coat mucilage of AtCESA1T166A mutant. Change in seed development was further reflected by a delayed germination and about 50% increase in the accumulation of proanthocyanidins, which is known to bind pectin and inhibit seed germination as revealed by previous studies. Taken together, the results suggest a role of AtCESA1 phosphorylation on T166 in modulating mucilage pectin synthesis and methylesterification as well as cellulose synthesis with a role in seed development.

Comparative Analysis of Herbaceous and Woody Cell Wall Digestibility by Pathogenic Fungi.

Fungal pathogens have evolved combinations of plant cell-wall-degrading enzymes (PCWDEs) to deconstruct host plant cell walls (PCWs). An understanding of this process is hoped to create a basis for improving plant biomass conversion efficiency into sustainable biofuels and bioproducts. Here, an approach integrating enzyme activity assay, biomass pretreatment, field emission scanning electron microscopy (FESEM), and genomic analysis of PCWDEs were applied to examine digestibility or degradability of selected woody and herbaceous biomass by pathogenic fungi. Preferred hydrolysis of apple tree branch, rapeseed straw, or wheat straw were observed by the apple-tree-specific pathogen Valsa mali, the rapeseed pathogen Sclerotinia sclerotiorum, and the wheat pathogen Rhizoctonia cerealis, respectively. Delignification by peracetic acid (PAA) pretreatment increased PCW digestibility, and the increase was generally more profound with non-host than host PCW substrates. Hemicellulase pretreatment slightly reduced or had no effect on hemicellulose content in the PCW substrates tested; however, the pretreatment significantly changed hydrolytic preferences of the selected pathogens, indicating a role of hemicellulose branching in PCW digestibility. Cellulose organization appears to also impact digestibility of host PCWs, as reflected by differences in cellulose microfibril organization in woody and herbaceous PCWs and variation in cellulose-binding domain organization in cellulases of pathogenic fungi, which is known to influence enzyme access to cellulose. Taken together, this study highlighted the importance of chemical structure of both hemicelluloses and cellulose in host PCW digestibility by fungal pathogens.

Wheat AGAMOUS LIKE 6 transcription factors function in stamen development by regulating the expression of Ta APETALA3.

Previous studies have revealed the functions of rice and maize AGAMOUS LIKE 6 (AGL6) genes OsMADS6 and ZAG3, respectively, in floral development; however, the functions of three wheat (Triticum aestivum) AGL6 genes are still unclear. Here, we report the main functions of wheat AGL6 homoeologous genes in stamen development. In RNAi plants, stamens showed abnormality in number and morphology, and a tendency to transform into carpels. Consistently, the expression of the B-class gene TaAPETALA3 (AP3) and the auxin-responsive gene TaMGH3 was downregulated, whereas the wheat ortholog of the rice carpel identity gene DROOPING LEAF was ectopically expressed in RNAi stamens. TaAGL6 proteins bind to the promoter of TaAP3 directly. Yeast one-hybrid and transient expression assays further showed that TaAGL6 positively regulates the expression of TaAP3 in vivo. Wheat AGL6 transcription factors interact with TaAP3, TaAGAMOUS and TaMADS13. Our findings indicate that TaAGL6 transcription factors play an essential role in stamen development through transcriptional regulation of TaAP3 and other related genes. We propose a model to illustrate the function and probable mechanism of this regulation. This study extends our understanding of AGL6 genes.

Hydrogen sulfide - cysteine cycle system enhances cadmium tolerance through alleviating cadmium-induced oxidative stress and ion toxicity in Arabidopsis roots.

Cadmium (Cd2+) is a common toxic heavy metal ion. We investigated the roles of hydrogen sulfide (H2S) and cysteine (Cys) in plant responses to Cd2+ stress. The expression of H2S synthetic genes LCD and DES1 were induced by Cd2+ within 3 h, and endogenous H2S was then rapidly released. H2S promoted the expression of Cys synthesis-related genes SAT1 and OASA1, which led to endogenous Cys accumulation. The H2S and Cys cycle system was stimulated by Cd2+ stress, and it maintained high levels in plant cells. H2S inhibited the ROS burst by inducing alternative respiration capacity (AP) and antioxidase activity. H2S weakened Cd2+ toxicity by inducing the metallothionein (MTs) genes expression. Cys promoted GSH accumulation and inhibited the ROS burst, and GSH induced the expression of phytochelatin (PCs) genes, counteracting Cd2+ toxicity. In summary, the H2S and Cys cycle system played a key role in plant responses to Cd2+ stress. The Cd2+ tolerance was weakened when the cycle system was blocked in lcddes1-1 and oasa1 mutants. This paper is the first to describe the role of the H2S and Cys cycle system in Cd2+ stress and to explore the relevant and specificity mechanisms of H2S and Cys in mediating Cd2+ stress.

[A FOLLOW-UP STUDY ON AUTOLOGOUS BONE MARROW MONONUCLEAR CELLS TRANSPLANTATION FOR CRITICAL LOWER ARTERIOSCLEROSIS OBLITERANS IN DIABETIC PATIENTS].

OBJECTIVE: To assess the long-term effectiveness and safety of autologous bone marrow mononuclear cells (BM-MNC) transplantation in the treatment of critical diabetic lower arteriosclerosis obliterans (ASO). METHODS: Between January 2007 and January 2010, 61 patients with critical diabetic lower ASO were treated with standard medical therapies in 29 cases (control group) or with standard medical therapies and autologous BM-MNC transplantation in 32 cases (treatment group). There was no significant difference in gender, age, disease duration, Fontatine stage, glucose (GLU), triglyceride (TG), total cholesterol (CHOL), low-density lipoprotein-cholesterol (LDL-C), hemoglobin Alc (HbA1c), systolic blood pressure (SBP), and diastolic blood pressure (DBP) between 2 groups (P > 0.05). The endpoints were overall survival (OS) and amputation-free survival (AFS). The risk indexes for ASO were observed and compared between 2 groups before and after treatments. RESULTS: The patients were followed up 2-36 months, and no malignant tumor occurred. The OS rate, OS time, AFS rate, and AFS time were 82.76% (24/29), (32.31 ± 9.08) months, 37.50% (9/24), and (21.28 ± 13.35) months in the control group and were 78.13% (25/32), (32.47 ± 6.96) months, 68.00% (17/25), and (28.38 ± 9.48) months in the treatment group; all indexes showed no significant differences (P > 0.05). OS rate, OS time, AFS rate, and AFS time showed no significant differences between 2 groups at the other time (P > 0.05) except AFS time at 1 year, which was significantly short in the control group than the treatment group (t = 2.806, P = 0.007). At the endpoint of follow-up, the indexes of GLU, TG, CHOL, LDL-C, HbAlc, SBP, and DBP showed no significant differences between before and after treatments and between 2 groups (P > 0.05) in 49 survival patients (24 in control group and 25 in treatment group). CONCLUSION: Autologous BM-MNC transplantation is safe and effective in the treatment of critical diabetic lower ASO, which can significantly improve AFS rate and prolong AFS time with no risks.