Rice blast, caused by Magnaporthe oryzae (M. oryzae), is one of the most destructive diseases threatening rice production worldwide. Development of resistant cultivars using broad-spectrum resistance (R) genes with high breeding value is the most effective and economical approach to control this disease. In this study, the breeding potential of Pigm gene in geng/japonica rice breeding practice in Jiangsu province was comprehensively evaluated. Through backcross and marker-assisted selection (MAS), Pigm was introduced into two geng rice cultivars (Wuyungeng 32/WYG32 and Huageng 8/HG8). In each genetic background, five advanced backcross lines with Pigm (ABLs) and the same genotypes as the respective recurrent parent in the other 13 known R gene loci were developed. Compared with the corresponding recurrent parent, all these ABLs exhibited stronger resistance in seedling inoculation assay using 184 isolates collected from rice growing regions of the lower region of the Yangtze River. With respect to panicle blast resistance, all ABLs reached a high resistance level to blast disease in tests conducted in three consecutive years with the inoculation of seven mixed conidial suspensions collected from different regions of Jiangsu province. In natural field nursery assays, the ABLs showed significantly higher resistance than the recurrent parents. No common change on importantly morphological traits and yield-associated components was found among the ABLs, demonstrating the introduction of Pigm had no tightly linked undesirable effect on rice economically important traits and its associated grain weight reduction effect could be probably offset by others grain weight genes or at least in the background of the aforementioned two varieties. Notably, one rice line with Pigm, designated as Yangnonggeng 3091, had been authorized as a new variety in Jiangsu province in 2021, showing excellent performance on both grain yield and quality, as well as the blast resistance. Together, these results suggest that the Pigm gene has a high breeding value in developing rice varieties with durable and broad-spectrum resistance to blast disease.

草害是影响作物高产、稳产、优质的重要因素之一,培育及推广抗除草剂水稻品种是最为经济有效的解决杂草问题的方式,目前江苏抗除草剂粳稻品种非常紧缺,无法适应农业生产中的用种需求.本研究综合评价了抗除草剂基因ALS627N在江苏粳稻育种实践中的育种应用潜力.通过连续回交结合分子标记辅助选择将金粳818中的ALS627N基因导入江苏省2个优良食味粳稻品种南粳5718和南粳505中,在每个遗传背景下选择3个背景与受体亲本基本一致、携带ALS627N的BC5 F5世代稳定改良品系,与受体亲本相比,ALS627N高世代回交改良系均表现出对咪唑啉酮类除草剂咪唑乙烟酸的完全抗性,表明在江苏省粳稻背景中导入ALS627N可以实现对除草剂的抗性.与受体亲本相比,ALS627N高世代回交改良系的农艺性状、产量及品质相关性状未发生一致变化,表明导入ALS627N对水稻重要经济性状没有带来不利影响.稻瘟病和白叶枯病抗性鉴定结果发现,ALS627N高世代回交改良系的穗颈瘟和白叶枯病抗性水平与受体亲本一致,表明导入ALS627N也不会影响稻瘟病和白叶枯病抗性.上述结果表明ALS627N基因在培育抗除草剂粳稻品种上具有很高的育种利用价值,得到的抗除草剂新品系不仅有望迅速服务于农业生产,还可以作为新的供体,加快江苏及其周边地区抗除草剂粳稻品种的开发.

Lesion-mimic mutants are useful materials to dissect mechanisms controlling programmed cell death (PCD) and defense response in plants. Although dozens of lesion-mimic mutant genes have been identified in plants, the molecular mechanisms underlying PCD and defense response remain to be extensively elucidated. Here, we identified a rice lesion mimic mutant, named lesion mimic 42 (lm42), from an ethylmethylsulfone (EMS)-induced mutant population. The lm42 mutant displayed flame-red spots on the leaves and sheaths at the 3-leaf developmental stage and exhibited impaired photosynthetic capacity with decreased chlorophyll content and decomposed chloroplast thylakoids. The lesion development of lm42 was light- and temperature-dependent. We identified a single base mutation (T38A), changing a Leu to Gln, in the first exon of LOC_Os12g16720 (LM42), which encodes a tryptamine 5-hydroxylase, by map-based cloning. We carried out transgenic complementation to confirm that this mutation caused the lm42 phenotype. We further knocked out the LM42 gene by CRISPR/Cas9 to recreate the lm42 phenotype. LM42 is highly expressed in leaves, leaf sheaths and roots. Loss-of-function of LM42 activated expression of ROS-generating genes and inhibited expression of ROS-scavenging genes, leading to ROS accumulation and eventually cell death. Furthermore, its disruption induced expression of defense-response genes and enhanced host resistance to both fungal pathogen Magnaporthe oryzae and bacterial pathogen Xanthomonas oryzae pv. oryzae. Our transcriptomic data suggested that the way lm42 led to lesion-mimic was probably by affecting ribosome development. Overall, our results demonstrate that tryptamine 5-hydroxylase-coding gene LM42 is required for suppression of cell death and uncontrolled activation of defense responses in rice.

[目的]明确水稻富含半胱氨酸类受体激酶(Cysteine-rich receptor-like kinases,CRK)家族基因对纹枯病菌侵染和植物激素的响应特征,是解析CRK在水稻纹枯病抗性中的功能的重要前期工作.[方法]利用生物信息学方法构建了水稻45个CRK的系统发育树,并利用qPCR分析了它们对纹枯病菌和对植物激素乙烯(Ethylene,ET)、茉莉酸(Jasmonic acid,JA)、水杨酸(Salicylic acid,SA)和细胞分裂素(Cytokinin,CK)等的响应特征,以及在水稻不同组织中的表达模式.[结果]水稻CRK家族可分为4个组,在染色体上成簇或紧密分布的CRK大部分来自同一组或同一分支.41个CRK响应纹枯病菌侵染,其中17个响应强烈;结合组织表达模式,发现这17个CRK基因中,CRK15、CRK23、CRK24、CRK26、CRK27、CRK28、CRK29、CRK30、CRK31和CRK33等10个基因在叶鞘和叶片中表达较强,暗示这些基因可能参与了对纹枯病的抗性;大部分同一分支的两个同源性较高的CRK对纹枯病菌的响应特征类似,表明这些CRK基因在调控纹枯病抗性上可能存在功能冗余.40个CRK对3种或4种植物激素均有响应,它们对不同激素的响应存在差异性,说明CRK可能广泛参与这些激素介导的防御信号途径;对JA和SA响应相反的有17个,对JA和SA、ET和JA、ET和SA响应类似的分别有21、21、23个.这不仅反映了ET、JA、SA信号途径间的协同和拮抗作用,也说明这些基因可能参与ET、JA和SA间的交互作用.[结论]鉴定到一些可能参与调控水稻纹枯病抗性的CRK基因,且它们可能在植物激素介导的防御途径中起作用.这为我们进一步探索CRK在调控水稻纹枯病抗性上的功能提供了科学线索.