Search

The plant hormone abscisic acid (ABA) is an important regulator of plant growth and development and plays a crucial role in both biotic and abiotic stress responses. ABA modulates flowering time, but the precise molecular mechanism remains poorly understood. Here we report that ABA INSENSITIVE 2 (ABI2) is the only phosphatase from the ABA-signaling core that positively regulates the transition to flowering in Arabidopsis. Loss-of-function abi2-2 mutant shows significantly delayed flowering both under long day and short day conditions. Expression of floral repressor genes such as FLOWERING LOCUS C (FLC) and CYCLING DOF FACTOR 1 (CDF1) was significantly up-regulated in abi2-2 plants while expression of the flowering promoting genes FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) was down-regulated. Through genetic interactions we further found that ost1-3 and abi5-1 mutations are epistatic to abi2-2 , as both of them individually rescued the late flowering phenotype of abi2-2. Interestingly, phosphorylation and protein stability of ABA INSENSITIVE 5 (ABI5) were enhanced in abi2-2 plants suggesting that ABI2 dephosphorylates ABI5, thereby reducing protein stability and the capacity to induce FLC expression. Our findings uncovered the unexpected role of ABI2 in promoting flowering by inhibiting ABI5-mediated FLC expression in Arabidopsis. [ABSTRACT FROM AUTHOR]

Sessile plants reprogram their metabolic and developmental processes during adaptation to prolonged environmental stresses. To understand the molecular mechanisms underlying adaptation of plant cells to saline stress, we established callus suspension cell cultures from Arabidopsis roots adapted to high salt for an extended period of time. Adapted cells exhibit enhanced salt tolerance compared with control cells. Moreover, acquired salt tolerance is maintained even after the stress is relieved, indicating the existence of a memory of acquired salt tolerance during mitotic cell divisions, known as mitotic stress memory. Metabolite profiling using 1H-nuclear magnetic resonance (NMR) spectroscopy revealed metabolic discrimination between control, salt-adapted and stress-memory cells. Compared with control cells, salt-adapted cells accumulated higher levels of sugars, amino acids and intermediary metabolites in the shikimate pathway, such as coniferin. Moreover, adapted cells acquired thicker cell walls with higher lignin contents, suggesting the importance of adjustments of physical properties during adaptation to elevated saline conditions. When stress-memory cells were reverted to normal growth conditions, the levels of metabolites again readjusted. Whereas most of the metabolic changes reverted to levels intermediate between salt-adapted and control cells, the amounts of sugars, alanine, γ-aminobutyric acid and acetate further increased in stress-memory cells, supporting a view of their roles in mitotic stress memory. Our results provide insights into the metabolic adjustment of plant root cells during adaptation to saline conditions as well as pointing to the function of mitotic memory in acquired salt tolerance. [ABSTRACT FROM AUTHOR]

Indole-3-acetic acid (IAA), a major plant auxin, is produced in both tryptophan-dependent and tryptophan-independent pathways. A major pathway in Arabidopsis thaliana generates IAA in two reactions from tryptophan. Step one converts tryptophan to indole-3-pyruvic acid (IPA) by tryptophan aminotransferases followed by a rate-limiting step converting IPA to IAA catalyzed by YUCCA proteins. We identified eight putative StYUC (Solanum tuberosum YUCCA) genes whose deduced amino acid sequences share 50%–70% identity with those of Arabidopsis YUCCA proteins. All include canonical, conserved YUCCA sequences: FATGY motif, FMO signature sequence, and FAD-binding and NADP-binding sequences. In addition, five genes were found with ~50% amino acid sequence identity to Arabidopsis tryptophan aminotransferases. Transgenic potato (Solanum tuberosum cv. Jowon) constitutively overexpressing Arabidopsis AtYUC6 displayed high-auxin phenotypes such as narrow downward-curled leaves, increased height, erect stature, and longevity. Transgenic potato plants overexpressing AtYUC6 showed enhanced drought tolerance based on reduced water loss. The phenotype was correlated with reduced levels of reactive oxygen species in leaves. The results suggest a functional YUCCA pathway of auxin biosynthesis in potato that may be exploited to alter plant responses to the environment. [ABSTRACT FROM AUTHOR]

Cellular Na+/K+ ratio is a crucial parameter determining plant salilxity stress resistance. We tested the function of plasma membrane Na+/K+ cotransporters in the High-affinity K+ Transporter (HKT) family from the halophytic Arabidopsis (Arabidopsis thaliana) relative Thelhmgiella salsuginea. T. salsuginea contains at least two HKT genes. TsHKT1;1 is expressed at very low levels, while the abundant TsHKT1;2 is transcriptionally strongly up-regulated by salt stress. TsHKT-based RNA interference in T. salsuginea resulted in Na+ sensitivity and K+ deficiency. The athktl mutant lines overexpressing TsHKT1;2 proved less sensitive to Na+ and showed less K+ deficiency than lines overexpressing AtHKT1. TsHKT1;2 ectopically expressed in yeast mutants lacking Na+ or K+ transporters revealed strong K+ transporter activity and selectivity for K+ over Na+. Altering two amino acid residues in TsHKT1;2 to mimic the AtHKT1 sequence resulted in enhanced sodium uptake and loss of the TsHKT1;2 intrinsic K+ transporter activity. We consider the maintenance of K+ uptake through TsHKT1;2 trader salt stress an important component supporting the halophytic lifestyle of T. salsuginea. [ABSTRACT FROM AUTHOR]

Introduction Once-daily administration of phosphodiesterase type 5 inhibitors has been shown to correct erectile dysfunction (ED). Aim To evaluate the long-term efficacy and safety after once-daily oral administration of udenafil 75 mg in men with ED. Methods This clinical trial was an open-label, fixed-dose, 24-week extension study (DA8159_EDDL_III) of a 24-week double-blinded efficacy and safety study of once-daily udenafil (parent study: DA8159_EDD_III). Subjects received udenafil 75 mg once daily for 24 weeks during this extension study, and the follow-up visit occurred during the 4-week ED treatment-free period. Main Outcome Measures Subjects were asked to complete the International Index of Erectile Function questionnaire and the Global Assessment Questionnaire at the 24-week extension and after the 4-week ED treatment-free period, and the development of adverse drug reactions was investigated. Results In total, 302 subjects were enrolled in this extension study. Improvement was shown with an increased erectile function (EF) domain score compared with baseline (14.60 ± 4.57) at extension week 48 (23.98 ± 5.44) and a slight increase in EF domain score compared with the last time point (week 24) of the parent study ( P < .001). The Global Assessment Questionnaire showed a high improvement rate of 95.4% at the extension 48-week time point. For shift to normal, almost half the subjects (45.1%) recovered “normal” EF, and 14.2% of subjects reported normal erections after the 4-week ED treatment-free period. The occurrence rate of adverse drug reactions was 8%, which consisted mainly of flushing and headache. Conclusion Once-daily dosing of udenafil 75 mg showed excellent efficacy and safety with long-term administration and allowed a more spontaneous sexual life. [ABSTRACT FROM AUTHOR]

Introduction The method of administration of oral phosphodiesterase-5 inhibitors has been expanded to once-daily repeated administration with lower initial dosage than on-demand administration. Aim The aim of this study was to evaluate the efficacy and safety of once-daily udenafil as a treatment for erectile dysfunction ( ED) for intermediate-term period. Methods This multicenter, randomized, double-blind clinical trial included 346 ED patients (placebo, udenafil 50 mg, udenafil 75 mg). Subjects were treated with each medication once daily for 24 weeks. Main Outcome Measures Subjects were asked to complete the International Index of Erectile Function ( IIEF)-erectile function ( EF) domain at baseline, 12 weeks, and 24 weeks and the development of adverse drug reactions ( ADRs) was inspected. Results Both dosages of udenafil induced a significant increase in IIEF- EF compared with placebo at both 12 and 24 weeks. When patients were divided according to the severity of baseline EF score, significant improvement was observed only with udenafil 75 mg regardless of the degree of ED. At 24 weeks, the proportions of patients who reported a return to normal EF ( IIEF- EF over 26) were 39.1% for udenafil 50 mg and 47.0% for udenafil 75 mg. In terms of safety, ADRs were observed in 6.1%, 12.9%, and 17.9% for placebo, udenafil 50 mg, and 75 mg, respectively. Although a statistically higher rate of ADRs was observed in the udenafil 75 mg group ( P = 0.024), the majority were mild and recovered without treatment. Conclusions Once-daily administration of udenafil 50 mg and 75 mg for 24 weeks resulted in improvement of EF. In particular, udenafil 75 mg improves EF regardless of the baseline degree of ED. Moon KH, Ko YH, Kim SW, Moon DG, Kim JJ, Park NC, Lee SW, Paick J-S, Ahn TY, Chung WS, Min KS, Park JK, Yang DY, and Park K. Efficacy of once-daily administration of udenafil for 24 weeks on erectile dysfunction: Results from a randomized multicenter placebo-controlled clinical trial. J Sex Med 2015;12:1194-1201. [ABSTRACT FROM AUTHOR]

Introduction. Mirodenafil is a newly developed oral phosphodiesterase type 5 inhibitor, currently under investigation as a treatment for erectile dysfunction (ED). Aim. We investigated the efficacy and safety of on demand mirodenafil therapy at fixed doses (50 and 100 mg) in Korean men with a broad range of ED. Methods. A multicenter, randomized, double-blind, placebo-controlled, parallel-group, fixed-dose study was conducted with 223 subjects who were randomized to placebo or mirodenafil at fixed doses of 50 or 100 mg for 12 weeks on an “as needed” basis. Main Outcome Measures. Primary efficacy measures were scores on the International Index of Erectile Function (IIEF) Question 3 (Q3) and Question 4 (Q4). Secondary efficacy measures included all domain scores of the IIEF, Sexual Encounter Profile Question 2 (SEP2), Sexual Encounter Profile Question 3 (SEP3), the Global Assessment Question (GAQ), and the Life Satisfaction Checklist (LSC). Safety assessments included laboratory tests, vital signs, physical examination, 12-lead electrocardiogram recordings, and patients’ reporting of adverse events. Results. Mirodenafil 50 and 100 mg groups showed a significantly greater increase in IIEF Q3 ( P = 0.0001, P < 0.0001, respectively) and Q4 scores (both P < 0.0001) at the end point compared with the placebo group. And mirodenafil in both doses significantly improved the scores of all five domains of the IIEF, SEP2, and SEP3 as well as the percentages of patients responding positively to the GAQ compared with the placebo group. As for LSC scores, the two mirodenafil groups showed significantly greater improvements in items regarding life as a whole, sexual life, and partner relationship than the placebo group. Most treatment-associated adverse events were of mild intensity, resolving spontaneously. Conclusions. Mirodenafil, in doses of 50 or 100 mg, significantly improved erectile function and were well tolerated in a representative population of Korean men with broad-spectrum ED of various etiologies and severities. Paick J-S, Ahn TY, Choi HK, Chung W-S, Kim JJ, Kim SC, Kim SW, Lee SW, Min KS, Moon KH, Park JK, Park K, Park NC, Suh J-K, Yang DY, and Jung H-G. Efficacy and safety of mirodenafil, a new oral phosphodiesterase type 5 inhibitor, for treatment of erectile dysfunction. J Sex Med 2008;5:2672–2680. [ABSTRACT FROM AUTHOR]