RLB (RICE LATERAL BRANCH) recruits PRC2-mediated H3K27 tri-methylation on OsCKX4 to regulate lateral branching.

Lateral branches such as shoot and panicle are determining factors and target traits for rice (Oryza sativa L.) yield improvement. Cytokinin promotes rice lateral branching; however, the mechanism underlying the fine-tuning of cytokinin homeostasis in rice branching remains largely unknown. Here, we report the map-based cloning of RICE LATERAL BRANCH (RLB) encoding a nuclear-localized, KNOX-type homeobox protein from a rice cytokinin-deficient mutant showing more tillers, sparser panicles, defected floret morphology as well as attenuated shoot regeneration from callus. RLB directly binds to the promoter and represses the transcription of OsCKX4, a cytokinin oxidase gene with high abundance in panicle branch meristem. OsCKX4 over-expression lines phenocopied rlb, which showed upregulated OsCKX4 levels. Meanwhile, RLB physically binds to Polycomb repressive complex 2 (PRC2) components OsEMF2b and co-localized with H3K27me3, a suppressing histone modification mediated by PRC2, in the OsCKX4 promoter. We proposed that RLB recruits PRC2 to the OsCKX4 promoter to epigenetically repress its transcription, which suppresses the catabolism of cytokinin, thereby promoting rice lateral branching. Moreover, antisense inhibition of OsCKX4 under the LOG promoter successfully increased panicle size and spikelet number per plant without affecting other major agronomic traits. This study provides insight into cytokinin homeostasis, lateral branching in plants, and also promising target genes for rice genetic improvement.

Posttranslational Modification of Waxy to Genetically Improve Starch Quality in Rice Grain.

The waxy (Wx) gene, encoding the granule-bound starch synthase (GBSS), is responsible for amylose biosynthesis and plays a crucial role in defining eating and cooking quality. The waxy locus controls both the non-waxy and waxy rice phenotypes. Rice starch can be altered into various forms by either reducing or increasing the amylose content, depending on consumer preference and region. Low-amylose rice is preferred by consumers because of its softness and sticky appearance. A better way of improving crops other than downregulation and overexpression of a gene or genes may be achieved through the posttranslational modification of sites or regulatory enzymes that regulate them because of their significance. The impact of posttranslational GBSSI modifications on extra-long unit chains (ELCs) remains largely unknown. Numerous studies have been reported on different crops, such as wheat, maize, and barley, but the rice starch granule proteome remains largely unknown. There is a need to improve the yield of low-amylose rice by employing posttranslational modification of Wx, since the market demand is increasing every day in order to meet the market demand for low-amylose rice in the regional area that prefers low-amylose rice, particularly in China. In this review, we have conducted an in-depth review of waxy rice, starch properties, starch biosynthesis, and posttranslational modification of waxy protein to genetically improve starch quality in rice grains.

Simultaneous degradation of aflatoxin B1 and zearalenone by Porin and Peroxiredoxin enzymes cloned from Acinetobacter nosocomialis Y1.

Mycotoxin contamination can cause severe health issues for both humans and animals. This study examined the potential of enzymes derived from Acinetobacter nosocomialis Y1 to simultaneously degrade aflatoxin B1 (AFB1) and zearalenone (ZEN), which could have significant implications in reducing mycotoxin contamination. Two enzymes, Porin and Peroxiredoxin, were identified with molecular weights of 27.8 and 20.8 kDa, respectively. Porin could completely degrade 2 µg/mL of AFB1 and ZEN within 24 h at 80 °C and 60 °C, respectively. Peroxiredoxin could completely degrade 2 µg/mL of AFB1 and reduce ZEN by 91.12% within 24 h. The addition of Na+, Cu2+, and K+ ions enhanced the degradation activities of both enzymes. LC-MS/MS analysis revealed that the molar masses of the degradation products of AFB1 and ZEN were 286 g/mol and 322.06 g/mol, and the products were identified as AFD1 and α or ß-ZAL, respectively. Vibrio fischeri bioluminescence assays further confirmed that the cytotoxicity of the two degradation products was significantly lower than that of AFB1 and ZEN. Based on these results, it can be inferred that the degradation product of ZEN is ß-ZAL. These findings suggest that both enzymes have the potential to be utilized as detoxification enzymes in food and feed.

Microbial Enzymes Involved in the Biotransformation of Major Mycotoxins.

Mycotoxins, the most researched biological toxins, can contaminate food and feed, resulting in severe health implications for humans and animals. Physical, chemical, and biological techniques are used to mitigate mycotoxin contamination. The biotransformation method using whole microbial cells or isolated enzymes is the best choice to mitigate mycotoxins. Using specific enzymes may avoid the disadvantages of utilizing a full microbe, such as accidental harm to the product's organoleptic characteristics and hazardous safety features. Moreover, the degradation rates of the isolated enzymes are higher than those of the whole-cell reactions, and they are substrate-specific. Their specificity is comprehensive and is shown at the positional and/or chiral center in many circumstances. Currently, only a few enzymes of microbial origin are commercially available. Therefore, there is a need to identify more novel enzymes of microbial origin that can mitigate mycotoxins. In this review, we conducted an in-depth summary of the microbial enzymes involved in the biotransformation of mycotoxins.

Identification of a Novel Bacillus velezensis IS-6 Nudix Hydrolase Nh-9 Involved in Ochratoxin A Detoxification by Transcriptomic Profiling and Functional Verification.

Contamination of foods and feeds with Ochratoxin A (OTA) is a global problem, and its detoxification is challenging. In this study, Bacillus velezensis IS-6 culture isolate supernatant degraded 1.5 g/mL OTA by 89% after 24 h of incubation at 37 °C, whereas viable cells and intra-cell extracts were less effective. The OTA degradation by B. velezensis IS-6 was an enzymatic process mediated by the culture supernatant. The degradation activity was optimal at 37 °C and pH 7.0, and Fe2+ and Cu2+ ions enhanced the OTA degradation. The LC-MS/MS analysis confirmed that structure of OTA was modified, resulting in the production of OTα that was less toxic than OTA. The transcriptomic analysis of B. velezensis IS-6 showed that 38 differentially expressed genes (DEGs) were significantly up-regulated, and 24 DEGs were down-regulated after treatment with OTA. A novel OTA degradation enzyme Nudix hydrolase Nh-9 was successfully cloned and characterized from the up-regulated genes. The recombinant Nh-9 enzyme was overexpressed in Escherichia coli BL21 and purified by affinity chromatography, exhibiting 68% degradation activity against 1.0 µg/mL OTA at 37 °C in 24 h. The degraded product by the Nh-9 enzyme was identified as the less toxic OTα by LC-MS/MS. According to the findings, it can be inferred that Nh-9 is the main OTA-degrading enzyme in B. velezensis IS-6. Furthermore, OTA may be co-degraded by Nh-9, carboxylesterase, signal peptidase, and other degrading agents that are yet to be discovered in this strain.

Distribution, accumulation, migration and risk assessment of trace elements in peanut-soil system.

Trace elements contamination is mainly originated from industrial emission, sewage irrigation and pesticides, and poses a threat to the environment and human health. This study analyzed the trace element pollutants in peanut-soil systems, the enrichment and translocation capacity of peanut to trace elements, and the potential risk of trace elements to environment and human health. The results indicated that Cd and Ni in peanut kernels exceeded the standard limits in 2019, and the exceeding rate were 9% and 31%, respectively. Cd in 8% of soil samples and As in 98% of soil samples exceeded the risk screening value of trace elements. The concentration of trace elements in peanuts was related to varieties and planting regions. In addition, there was a significant positive correlation between the concentration of Cd in peanut kernel and its concentration in soil. Compared with other trace elements, peanut kernels had stronger ability to enrich and transport Cd, Cu, and Zn, the BFs were 0.45, 0.51 and 0.47, respectively. After oil extraction, trace elements were mainly concentrated in peanut meal, and only 0.25% of Cd was in oil. The RI of trace elements was less than 150, indicating that the study area was under low degree of ecological risk. However, As and Cd might pose moderate risk to environment. Trace elements in soil and peanut could not cause non-carcinogenic and carcinogenic risks to human, but the HI and CR value of As (0.59 and 9.54 × 10-5) in soil and CRing value of Cd (9.25 × 10-7) in peanut were close to the critical value. We conclude that Cd pollution in peanut kernel, and Cd and As pollution in soil should be monitored to enter into the food chain or environment and to avoid the possible health hazards and environment risks.

Verification and dissection of one quantitative trait locus for grain size and weight on chromosome 1 in rice.

Grain size and weight are the key traits determining rice quality and yield and are mainly controlled by quantitative trait loci (QTL). In this study, one minor QTL that was previously mapped in the marker interval of JD1009-JD1019 using the Huanghuazhan/Jizi1560 (HHZ/JZ1560) recombinant inbred line (RIL) population, qTGW1-2, was validated to regulate grain size and weight across four rice-growing seasons using twenty-one near isogenic line (NIL)-F2 populations. The twenty-one populations were in two types of genetic background that were derived from the same parents HHZ and JZ1560. Twelve F9, F10 or F11 NIL-F2 populations with the sequential residual heterozygous regions covering JD1009-RM6840 were developed from one residual heterozygote (RH) in the HHZ/JZ1560 RIL population, and the remaining nine BC3F3, BC3F4 or BC3F5 NIL-F2 populations with the sequential residual heterozygous regions covering JD1009-RM6840 were constructed through consecutive backcrosses to the recurrent parent HHZ followed with marker assistant selection in each generation. Based on the QTL analysis of these genetic populations, qTGW1-2 was successfully confirmed to control grain length, width and weight and further dissected into two QTLs, qTGW1-2a and qTGW1-2b, which were respectively narrowed down to the marker intervals of JD1139-JD1127 (~ 978.2-kb) and JD1121-JD1102 (~ 54.8-kb). Furthermore, the two types of NIL-F2 populations were proved to be able to decrease the genetic background noise and increase the detection power of minor QTL. These results provided an important basis for further map-based cloning and molecular design breeding with the two QTLs in rice.

bZIP72 promotes submerged rice seed germination and coleoptile elongation by activating ADH1.

Seed germination and coleoptile elongation in response to flooding stress is an important trait for the direct seeding of rice. However, the genes regulating this process and the underlying mechanisms are little understood. In this study, bZIP72 was identified as a positive regulator of seed germination under submergence. Transcription of bZIP72 was submergence induced. Over-expression of bZIP72 enhanced submerged seed germination and coleoptile elongation, while bzip72 mutants exhibited the opposite tendency. Using biochemical interaction assays, we showed that bZIP72 directly binds to the promoter of alcohol dehydrogenase 1 (ADH1), enhances its activity, and subsequently produces more NAD+, NADH and ATP involved in the alcoholic fermentation and glycolysis pathway, ultimately providing necessary energy reserves thus conferring tolerance to submergence. In summary, this research provides novel insights into bZIP72 participation in submerged rice seed germination and coleoptile elongation.