Ectopic Expression of OsJAZs Alters Plant Defense and Development.

A key step in jasmonic acid (JA) signaling is the ligand-dependent assembly of a coreceptor complex comprising the F-box protein COI1 and JAZ transcriptional repressors. The assembly of this receptor complex results in proteasome-mediated degradation of JAZ repressors, which in turn bind and repress MYC transcription factors. Many studies on JAZs have been performed in Arabidopsis thaliana, but the function of JAZs in rice is largely unknown. To systematically reveal the function of OsJAZs, in this study, we compared the various phenotypes resulting from 13 OsJAZs via ectopic expression in Arabidopsis thaliana and the phenotypes of 12 AtJAZs overexpression (OE) lines. Phylogenetic analysis showed that the 25 proteins could be divided into three major groups. Yeast two-hybrid (Y2H) assays revealed that most OsJAZ proteins could form homodimers or heterodimers. The statistical results showed that the phenotypes of the OsJAZ OE plants were quite different from those of AtJAZ OE plants in terms of plant growth, development, and immunity. As an example, compared with other JAZ OE plants, OsJAZ11 OE plants exhibited a JA-insensitive phenotype and enhanced resistance to Pst DC3000. The protein stability after JA treatment of OsJAZ11 emphasized the specific function of the protein. This study aimed to explore the commonalities and characteristics of different JAZ proteins functions from a genetic perspective, and to screen genes with disease resistance value. Overall, the results of this study provide insights for further functional analysis of rice JAZ family proteins.

Purification and antioxidant capacity analysis of anthocyanin glucoside cinnamic ester isomers from Solanum nigrum fruits.

In a recent study, anthocyanins, which have a strong free radical-scavenging activity, were examined for their potential to effectively prevent cancer. However, clinical trials are limited by the purity of the anthocyanin. Multiple methods are used to extract and purify anthocyanins. Based on previous work on Solanum nigrum, which is a widely distributed plant, in this study, DM130 macroporous resin, Sephadex LH20, and a C18 column were used to separate cis-trans anthocyanin isomers. These anthocyanins constitute the majority of total S. nigrum anthocyanins. The results showed that this "DM130-LH20-C18 system" can be used to obtain a cinnamic acid-derived cis-trans anthocyanin, petunidin-3-(p-coumaroyl)-rutinoside-5-glucoside, with a purity of 98.5%, for effective quantitation. In order to determine the antioxidant ability of the petunidin-3-(p-coumaroyl)-rutinoside-5-glucoside cis-trans isomers, three ordinary methods were adopted. The maximum antioxidant ability of the cis-trans anthocyanin was dozens of times higher than that of vitamin C.

Identification of the phytosulfokine receptor 1 (OsPSKR1) confers resistance to bacterial leaf streak in rice.

MAIN CONCLUSION: A rice allele of PSKR1 functioning in resistance to bacterial leaf streak was identified. Phytosulfokine (PSK), a disulfated pentapeptide encoded by precursor genes that are ubiquitously present in higher plants, belongs to the group of plant peptide growth factors. The PSK receptor PSKR1 in Arabidopsis thaliana is an active kinase and has guanylate cyclase activity resulting in dual-signaling outputs. Here, the LOC_Os02g41890 out of three candidates completely rescued root growth and susceptible to Pseudomonas syringae pv. DC3000 in the Arabidopsis pskr1-3 mutant and was identified as OsPSKR1. This protein was localized to plasma membrane similar to AtPSKR1. The expression of OsPSKR1 was upregulated upon inoculation with RS105, a strain of Xanthomonas oryzae pv. oryzicola (Xoc) that cause bacterial leaf streak in rice. OsPSKR1 overexpression (OE) lines had greater resistance to RS105 than the wild type. Consistently, the expression of pathogenesis-related genes involved in the salicylic acid (SA) pathway was upregulated in the transgenic lines. Overall, OsPSKR1 functions as a candidate PSK receptor and regulates resistance to Xoc by activating the expression of pathogenesis-related genes involved in the SA pathway in rice.

OsHsfB4d Binds the Promoter and Regulates the Expression of OsHsp18.0-CI to Resistant Against Xanthomonas Oryzae.

BACKGROUND: Bacterial leaf streak (BLS) and bacterial blight (BB) are two major prevalent and devastating rice bacterial diseases caused by the Gram-negative bacteria of Xanthomonas oryzae pv. oryzicola (Xoc) and Xanthomonas oryzae pv. oryzae (Xoo), respectively. Previously, we identified a defence-related (DR) gene encoding a small heat shock protein, OsHsp18.0-CI, that positively regulates BLS and BB resistance in rice. RESULTS: To reveal the regulatory mechanism of the OsHsp18.0-CI response to Xoc and Xoo, we characterized the class B heat shock factor (Hsf), OsHsfB4d, through transcriptional analysis and a transgenic study. OsHsfB4d is upregulated post inoculation by either the Xoc strain RS105 or Xoo strain PXO99a in Zhonghua 11 (wild type, ZH11) as well as in OsHsp18.0-CI overexpressing rice plants. Transient expression of OsHsfB4d can activate the expression of green fluorescent protein (GFP) and luciferase (Luc) via the OsHsp18.0-CI promoter. Rice plants overexpressing OsHsfB4d exhibited enhanced resistance to RS105 and PXO99a as well as increased expression of OsHsp18.0-CI and pathogenesis-related genes. Furthermore, we found that OsHsfB4d directly binds to a DNA fragment carrying the only perfect heat shock element (HSE) in the promoter of OsHsp18.0-CI. CONCLUSION: Overall, we reveal that OsHsfB4d, a class B Hsf, acts as a positive regulator of OsHsp18.0-CI to mediate BLS and BB resistance in rice.