Genome-wide association mapping for resistance to bacterial blight and bacterial leaf streak in rice.

MAIN CONCLUSION: Using genome-wide SNP association mapping, a total of 77 and 7 loci were identified for rice bacterial blight and bacterial leaf streak resistance, respectively, which may facilitate rice resistance improvement. Bacterial blight (BB) and bacterial leaf streak (BLS) caused by Gram-negative bacteria Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), respectively, are two economically important diseases negatively affecting rice production. To mine new sources of resistance, a set of rice germplasm collection consisting of 895 re-sequenced accessions from the 3000 Rice Genomes Project (3 K RGP) were screened for BB and BLS resistance under field conditions. Higher levels of BB resistance were observed in aus/boro subgroup, whereas the japonica, temperate japonica and tropical japonica subgroups possessed comparatively high levels of resistance to BLS. A genome-wide association study (GWAS) mined 77 genomic loci significantly associated with BB and 7 with BLS resistance. The phenotypic variance (R2) explained by these loci ranged from 0.4 to 30.2%. Among the loci, 7 for BB resistance were co-localized with known BB resistance genes and one for BLS resistance overlapped with a previously reported BLS resistance QTL. A search for the candidates in other novel loci revealed several defense-related genes that may be involved in resistance to BB and BLS. High levels of phenotypic resistance to BB or BLS could be attributed to the accumulation of the resistance (R) alleles at the associated loci, indicating their potential value in rice resistance breeding via gene pyramiding. The GWAS analysis validated the known genes underlying BB and BLS resistance and identified novel loci that could enrich the current resistance gene pool. The resources with strong resistance and significant SNPs identified in this study are potentially useful in breeding for BB and BLS resistance.

Mechanistic analysis of thermal stability in a novel thermophilic polygalacturonase MlPG28B derived from the marine fungus Mucor lusitanicus.

In this study, heterologous MlPG28B expression was obtained by cloning the Mucor lusitanicus gene screened from a marine environment. The enzyme activity of MlPG28B was maximum at 60 °C, 30 % of the enzyme activity was retained after incubation at 100 °C for 30 min, and enzyme activity was still present after 60 min incubation, one of the best thermostable polygalacturonases characterized until now. The high-purity oligosaccharide standards (DP2-DP7) were prepared with polygalacturonic acid as a substrate. Kinetic parameters showed that MlPG28B at the optimum temperature has a low Km value (3055 ± 1104 mg/L), indicating high substrate affinity. Sequence alignment analysis inferred key residues Cys276, Cys284, Lys107, and Gln237 for MlPG28B thermal stability. Molecular docking and molecular dynamics simulation results indicated that MlPG28B has flexible T1 and T3 loops conducive to substrate recognition, binding, and catalysis and forms a hydrogen bond to the substrate by a highly conserved residue Asn161 in the active-site cleft. Based on site-directed mutation results, the five residues are key in determining MlPG28B thermal stability. Therefore, MlPG28B is a promising candidate for industrial enzymes in feed preparation.

Effect of various different pretreatment methods on infrared combined hot air impingement drying behavior and physicochemical properties of strawberry slices.

In current work, the effect of freezing (F), ultrasound (U), and freeze- ultrasound (FU) pretreatment on infrared combined with hot air impingement drying kinetics, cell ultrastructure, enzyme activity, and physicochemical properties of strawberry slices were explored. Results showed that FU pretreatment enhanced cell membrane permeability via forming micropores, altered water status by transforming bound water into free water and thus promoted moisture diffusivity and decreased drying time by 50% compared to the control group. FU pretreatment also extensively decreased pectin methylesterase enzyme activity and maintained quality. The contents of total phenols, anthocyanins, vitamin C, antioxidant activity, and a* value of dried strawberries pretreated by FU were extensively increased compared to the control group. U and FU pretreatments were beneficial for retaining aromatic components and organic sulfides according to e-nose analyses. The findings indicate that FU is a promising pretreatment technique as it enhances drying process and quality of strawberry slices.

Resistance Genes and their Interactions with Bacterial Blight/Leaf Streak Pathogens (Xanthomonas oryzae) in Rice (Oryza sativa L.)-an Updated Review.

Rice (Oryza sativa L.) is a staple food crop, feeding more than 50% of the world's population. Diseases caused by bacterial, fungal, and viral pathogens constantly threaten the rice production and lead to enormous yield losses. Bacterial blight (BB) and bacterial leaf streak (BLS), caused respectively by gram-negative bacteria Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), are two important diseases affecting rice production worldwide. Due to the economic importance, extensive genetic and genomic studies have been conducted to elucidate the molecular mechanism of rice response to Xoo and Xoc in the last two decades. A series of resistance (R) genes and their cognate avirulence and virulence effector genes have been characterized. Here, we summarize the recent advances in studies on interactions between rice and the two pathogens through these R genes or their products and effectors. Breeding strategies to develop varieties with durable and broad-spectrum resistance to Xanthomonas oryzae based on the published studies are also discussed.

[Comparison study of infantile tuina between LI Dexiu and LIU Kaiyun].

With esoterica of Infantile Tuina by LI Dexiu and Infantile Tuina Therapy of LIU Kaiyun, the differences and similarities of manipulations, acupoints and the principles of treatment were studied so as to provide theoretical evidence to popularize tuina of LI Dexiu and LIU Kaiyun.