Search

Summary: Bacterial leaf streak (BLS) is a major bacterial disease of rice. Utilization of host genetic resistance has become one of the most important strategies for controlling BLS. However, only a few resistance genes have been characterized. Previously, a recessive BLS resistance gene bls1 was roughly mapped on chromosome 6. Here, we further delineated bls1 to a 21 kb region spanning four genes. Genetic analysis confirmed that the gene encoding a mitogen‐activated protein kinase (OsMAPK6) is the target of the allelic genes BLS1 and bls1. Overexpression of BLS1 weakened resistance to the specific Xanthomonas oryzae pv. oryzicola (Xoc) strain JZ‐8, while low expression of bls1 increased resistance. However, both overexpression of BLS1 and low expression of bls1 could increase no‐race‐specific broad‐spectrum resistance. These results indicate that BLS1 and bls1 negatively regulate race‐specific resistance to Xoc strain JZ‐8 but positively and negatively control broad‐spectrum resistance, respectively. Subcellular localization demonstrated that OsMAPK6 was localized in the nucleus. RGA4, which is known to mediate resistance to Xoc, is the potential target of OsMAPK6. Overexpression of BLS1 and low expression of bls1 showed increase in salicylic acid and induced expression of defense‐related genes, simultaneously increasing broad‐spectrum resistance. Moreover, low expression of bls1 showed increase an in jasmonic acid and abscisic acid, in company with an increase in resistance to Xoc strain JZ‐8. Collectively, our study provides new insights into the understanding of BLS resistance and facilitates the development of rice host‐resistant cultivars. Significance Statement: A recessive bacterial leaf streak resistance gene bls1, which encodes a mitogen‐activated protein kinase (OsMAPK6), was cloned from common wild rice. The gene bls1 and its dominant allele BLS1 negatively regulate race‐specific resistance to Xanthomonas oryzae pv. oryzicola strain JZ‐8, but negatively and positively control broad‐spectrum resistance, respectively. [ABSTRACT FROM AUTHOR]

Summary: Anthocyanins play an important role in the growth of plants, and are beneficial to human health. In plants, the MYB‐bHLH‐WD40 (MBW) complex activates the genes for anthocyanin biosynthesis. However, in rice, the WD40 regulators remain to be conclusively identified. Here, a crucial anthocyanin biosynthesis gene was fine mapped to a 43.4‐kb genomic region on chromosome 2, and a WD40 gene OsTTG1 (Oryza sativa TRANSPARENT TESTA GLABRA1) was identified as ideal candidate gene. Subsequently, a homozygous mutant (osttg1) generated by CRISPR/Cas9 showed significantly decreased anthocyanin accumulation in various rice organs. OsTTG1 was highly expressed in various rice tissues after germination, and it was affected by light and temperature. OsTTG1 protein was localized to the nucleus, and can physically interact with Kala4, OsC1, OsDFR and Rc. Furthermore, a total of 59 hub transcription factor genes might affect rice anthocyanin biosynthesis, and LOC_Os01g28680 and LOC_Os02g32430 could have functional redundancy with OsTTG1. Phylogenetic analysis indicated that directional selection has driven the evolutionary divergence of the indica and japonica OsTTG1 alleles. Our results suggest that OsTTG1 is a vital regulator of anthocyanin biosynthesis, and an important gene resource for the genetic engineering of anthocyanin biosynthesis in rice and other plants. Significance Statement: Anthocyanins have an important health care effect on human health. Thus, it is very important to explore the biosynthesis of anthocyanins in rice. We reported the map‐based cloning and characterization of OsTTG1, a key gene that regulates the anthocyanin biosynthesis in various rice organs. Our findings provide an understanding of the regulation of the plant anthocyanin biosynthesis. [ABSTRACT FROM AUTHOR]