Lesion mimic mutants spontaneously produce disease spots in the absence of biotic or abiotic stresses. Analyzing lesion mimic mutants’ sheds light on the mechanisms underlying programmed cell death and defense-related responses in plants. Here, we isolated and characterized the rice (Oryza sativa) spotted leaf 36 (spl36) mutant, which was identified from an ethyl methanesulfonate-mutagenized japonica cultivar Yundao population. spl36 displayed spontaneous cell death and enhanced resistance to rice bacterial pathogens. Gene expression analysis suggested that spl36 functions in the disease response by upregulating the expression of defense-related genes. Physiological and biochemical experiments indicated that more cell death occurred in spl36 than the wild type and that plant growth and development were affected in this mutant. We isolated SPL36 by map-based cloning. A single base substitution was detected in spl36, which results in a cysteine-to-arginine substitution in SPL36. SPL36 is predicted to encode a receptor-like protein kinase containing leucine-rich domains that may be involved in stress responses in rice. spl36 was more sensitive to salt stress than the wild type, suggesting that SPL36 also negatively regulates the salt-stress response. These findings suggest that SPL36 regulates the disease resistance response in rice by affecting the expression of defense- and stress-related genes.

Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 is the third generation of novel targeted genome editing technology after zinc finger nucleases (ZFNs) and transcription activator like effector nucleases (TALENs). It is also one of the most promising techniques for mutating and modifying genes. The CRISPR-Cas9 system has the advantages of simplicity, high efficiency, high specificity, and low production cost, thus greatly promoting the study of gene function. Meanwhile, it has attracted the attention of biologists. After the development and improvement in recent years, CRISPR-Cas9 system has become increasingly mature and has been widely used in crop improvement. Firstly, this review systematically summarizes the generation and advantages of CRISPR-Cas9 system. Secondly, three derivative technologies of the CRISPR-Cas9 system are introduced. Thirdly, this review focuses on the application of CRISPR-Cas9 system in gene knockout, gene knock-in, and gene regulation, as well as the improvement of yield, quality, and biological resistance of important crops such as rice, wheat, soybean, corn, and potato. Finally, this review proposes the potential challenges of CRISPR-Cas9 system, and discusses the future development of CRISPR-Cas9 system.

Rice (Oryza sativa) spikelets are a unique inflorescence structure and their development directly determines grain size and yield. Although many genes related to spikelet development have been reported, the molecular mechanisms underlying this process have not been fully elucidated. In this study, we identified a new recessive rice mutant, lacking rudimentary glume 1 (lrg1). The lrg1 spikelets only formed one rudimentary glume, which, along with the sterile lemmas, was homeotically transformed into lemma-like organs and acquired lemma identity. The transition from the spikelet to the floral meristem was delayed in the lrg1 mutant, resulting in the formation of an ectopic lemma-like organ between the sterile lemma and the terminal floret. In addition, we found that the abnormal lrg1 grain phenotype resulted from the alteration of cell numbers and the hull size. LRG1 encodes a ZOS4-06-C2H2 zinc-finger protein with the typical EAR motifs, and is expressed in all organs and tissues. LRG1 localizes to the nucleus and can interact with the TOPLESS-RELATED PROTEINs (TPRs) to repress the expressions of their downstream target genes. Taken together, our results reveal that LRG1 plays an important role in the regulation of spikelet organ identity and grain size.

As one of the most important food crops in the world, rice yield is directly related to national food security. Lodging is one of the most important factors restricting rice production, and the cultivation of rice varieties with lodging resistance is of great significance in rice breeding. The lodging resistance of rice is directly related to the mechanical strength of the stalks. In this paper, we reviewed the cell wall structure, its components, and its genetic regulatory mechanism, which improved the regulatory network of rice stalk mechanical strength. Meanwhile, we analyzed the new progress in genetic breeding and put forward some scientific problems that need to be solved in this field in order to provide theoretical support for the improvement and application of rice breeding.