Genome-wide analysis of dirigent gene family in pepper (Capsicum annuum L.) and characterization of CaDIR7 in biotic and abiotic stresses.

The dirigent (DIR and DIR-like) proteins involved in lignification, play a pivotal role against biotic and abiotic stresses in plants. However, no information is available about DIR gene family in pepper (Capsicum annuum L.). In this study, 24 putative dirigent genes (CaDIRs) were identified, their gene structure, genome location, gene duplication and phylogenetic relationship were elucidated. Tissue-specific expression analysis displayed the highest transcription levels in flower, stem and leaf. Some CaDIRs were up-regulated by virulent (CaDIR2, 3, 6, 7, 11, 14, 16, 22 and 23) and avirulent (CaDIR3, 5, 7, 16, 20, 22, 23 and 24) Phytophthora capsici strains, as well as by Methyl jasmonate, salicylic acid, NaCl and mannitol stresses. Acid-soluble lignin content increased (103.21%) after P. capsici inoculation (48-hour). Silencing of CaDIR7 weakened plant defense by reducing (~50%) root activity and made plants more susceptible (35.7%) to P. capsici and NaCl (300 mM). Leaf discs of the CaDIR7:silenced plants exposed to NaCl and mannitol (300 mM each), exhibited a significant decrease (56.25% and 48% respectively) in the chlorophyll content. These results suggested that CaDIR7 is involved in pepper defense response against pathogen and abiotic stresses and the study will provide basic insights for future research regarding CaDIRs.

Cyclooxygenase-2 expression is positively associated with lymph node metastasis in nasopharyngeal carcinoma.

BACKGROUND: Accumulating evidence has demonstrated that cyclooxygenase-2 (COX-2) is involved in head and neck cancers, especially in nasopharyngeal carcinoma (NPC). However, the association between COX-2 expression and lymph node metastasis in NPC remains uncertain. This systematic review and meta-analysis meta-analysis investigated the relationship between COX-2 expression and lymph node metastasis and other signs of disease progression in NPC. METHODS: Previously published studies assessing COX-2 expression and lymph node metastasis in NPC were identified in four English databases and three Chinese ones (Pubmed, Embase, Cochrane Database of Systematic Reviews, Web of Science, China National Knowledge Infrastructure, Wanfang, Vip Journal Integration Platform) up to November 2016. Quality of all eligible studies was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS). Pooled odds ratios (OR) and their 95% confidence intervals (95%CI) were calculated with fixed-effects or random-effects model to evaluate the effects of COX-2 expression on lymph node metastasis. RESULTS: A total of 27 studies with 1797 NPC patients met the inclusion criteria. The expression of COX-2 was significantly higher in patients with nasopharyngeal carcinoma than those without the carcinoma, with a combined OR of 21.17 (95%CI = 15.02-29.85, I2 = 35.1%, Pheterogeneity = 0.070). A statistically significant association between COX-2 expression and lymph node metastasis in NPC patients, with an OR of 4.44 (95%CI = 3.46-5.70, I2 = 38.3%, Pheterogeneity = 0.024), and with other indicators of disease progression. Subgroup analyses based on COX-2 assay and staging criteria of TNM showed no significant heterogeneity. CONCLUSIONS: The results suggest that expression of COX-2 is associated with lymph node metastasis and disease progression in NPC, indicating a potential role in evaluation of prognosis and in treatment decisions. COX-2 inhibitors have potential in the treatment of NPC that should be further investigated.

Characteristic of the pepper CaRGA2 gene in defense responses against Phytophthora capsici Leonian.

The most significant threat to pepper production worldwide is the Phytophthora blight, which is caused by the oomycete pathogen, Phytophthora capsici Leonian. In an effort to help control this disease, we isolated and characterized a P. capsici resistance gene, CaRGA2, from a high resistant pepper (C. annuum CM334) and analyzed its function by the method of real-time PCR and virus-induced gene silencing (VIGS). The CaRGA2 has a full-length cDNA of 3,018 bp with 2,874 bp open reading frame (ORF) and encodes a 957-aa protein. The protein has a predicted molecular weight of 108.6 kDa, and the isoelectric point is 8.106. Quantitative real-time PCR indicated that CaRGA2 expression was rapidly induced by P. capsici. The gene expression pattern was different between the resistant and susceptible cultivars. CaRGA2 was quickly expressed in the resistant cultivar, CM334, and reached to a peak at 24 h after inoculation with P. capsici, five-fold higher than that of susceptible cultivar. Our results suggest that CaRGA2 has a distinct pattern of expression and plays a critical role in P. capsici stress tolerance. When the CaRGA2 gene was silenced via VIGS, the resistance level was clearly suppressed, an observation that was supported by semi-quantitative RT-PCR and detached leave inoculation. VIGS analysis revealed their importance in the surveillance to P. capsici in pepper. Our results support the idea that the CaRGA2 gene may show their response in resistance against P. capsici. These analyses will aid in an effort towards breeding for broad and durable resistance in economically important pepper cultivars.

A Novel Peroxidase CanPOD Gene of Pepper Is Involved in Defense Responses to Phytophtora capsici Infection as well as Abiotic Stress Tolerance.

Peroxidases are involved in many plant processes including plant defense responses to biotic and abiotic stresses. We isolated a novel peroxidase gene CanPOD from leaves of pepper cultivar A3. The full-length gene has a 1353-bp cDNA sequence and contains an open reading frame (ORF) of 975-bp, which encodes a putative polypeptide of 324 amino acids with a theoretical protein size of 34.93 kDa. CanPOD showed diverse expression levels in different tissues of pepper plants. To evaluate the role of CanPOD in plant stress responses, the expression patterns of CanPOD were examined using Real-Time RT-PCR. The results indicated that CanPOD was significantly induced by Phytophtora capsici. Moreover, CanPOD was also up-regulated in leaves after salt and drought stress treatments. In addition, CanPOD expression was strongly induced by signaling hormones salicylic acid (SA). In contrast, CanPOD was not highly expressed after treatment with cold. Meanwhile, in order to further assess the role of gene CanPOD in defense response to P. capsici attack, we performed a loss-of-function experiment using the virus-induced gene silencing (VIGS) technique in pepper plants. In comparison to the control plant, the expression levels of CanPOD were obviously decreased in CanPOD-silenced pepper plants. Furthermore, we analyzed the effect of P. capsici on detached-leaves and found that the CanPOD-silenced plant leaves were highly susceptible to P. capsici infection. Taken together, our results suggested that CanPOD is involved in defense responses to P. capsici infection as well as abiotic stresses in pepper plants.

[Histological and cytological study on the ontogeny of embryoid in pepper anther culture].

The characteristics of histology and cytology of embryogenesis in pepper anther culture were examined with fluorescence microscopy, scanning microscopy, and electron microscopy. Pepper was characterized by a strong asynchrony of pollen development within a single anther. With the change of culture period, the proportion of dead pollen increased drastically from 2 day after culture. Microspores that were cultured at the late-uninucleate stage followed one of two developmental pathways. In the more common route, the first sporophytic division was asymmetric and produced what appeared to be typical bicellular pollen. Embryogenic pollen was formed by repeated divisions of the vegetative nuclei. An exine with its specific pattern had already been formed, when microspores were released from tetrads. During subsequent pollen development, microspores increased in size and continued to strengthen the exine. After 24 h in culture, the microspores had increased in size. Thereafter, embryogenesis was indicated in some microspores by two different morphological changes. One featured an expansion in volume of the cell cluster around the germination aperture, the other showed cell cluster volume expansion over the entire microspore surface. Morphogenesis of microspore-derived embryos has been analyzed, at both light and electron microscopical levels. The changes in cell organization after embryogenesis induction, and the characterization of the time sequence of a set of structural events, had been also explained. These changes mainly affected the plastids, the vacuolar compartment, the cell wall and the nucleus. Further differentiation processes mimicked that of the zygotic development.