Plant Gene and Trait 2024, Vol.15, No.2, 73-84 http://genbreedpublisher.com/index.php/pgt 75 rachis and primary and secondary branches, resulting in a dense and erect panicle phenotype without significantly altering grain production (Li et al., 2010). These findings highlight the diverse roles of DEP1 and its variants in modulating panicle architecture and grain yield in rice. 3 Genetic Modulation of DEP1 3.1 Techniques for modulating DEP1 expression The genetic modulation of the DENSE AND ERECT PANICLE 1 (DEP1) gene has been a focal point in rice breeding due to its significant impact on panicle architecture and grain yield. Various techniques have been employed to modulate DEP1 expression, including natural variation, induced mutations, and gene editing. Natural variation at the DEP1 locus has been a key source of genetic diversity. A dominant allele at the DEP1 locus, which is a gain-of-function mutation, has been identified to enhance meristematic activity, leading to a reduced length of the inflorescence internode and an increased number of grains per panicle (Huang et al., 2009). This allele is prevalent in many high-yielding Chinese rice varieties and has also been found in temperate cereals, indicating its evolutionary significance. Induced mutations have also been utilized to study and exploit DEP1. For instance, the dep3 mutant, derived from the Japonica cultivar Hwacheong treated with N-methyl-N-nitrosourea, exhibits a dense and erect panicle phenotype. The DEP3 gene, identified through map-based cloning, encodes a patatin-like phospholipase A2 (PLA2) superfamily domain-containing protein, and the mutation involves a 408 bp genomic deletion (Qiao et al., 2011). Gene editing technologies, such as CRISPR/Cas9, have provided precise tools for modulating DEP1. A study demonstrated the use of CRISPR/Cas9 to create an erect panicle mutant at the DEP1 locus, which resulted in improved canopy structure and increased biomass under low fertilization conditions (Fei et al., 2019). This approach not only elucidates the functional role of DEP1 but also offers practical applications in sustainable agriculture. 3.2 Impacts of genetic alterations of DEP1 on rice yield Genetic alterations of DEP1 have profound impacts on rice yield, primarily through modifications in panicle architecture. The gain-of-function mutation at the DEP1 locus enhances grain yield by increasing the number of grains per panicle. This mutation is associated with a reduced length of the inflorescence internode and increased meristematic activity, which collectively contributes to higher grain production (Huang et al., 2009). The dep3 mutant, characterized by a dense and erect panicle, also shows significant changes in panicle traits, including panicle length, grain shape, and grain number per panicle. The mutation leads to more small vascular bundles and a thicker culm, which support the erect panicle phenotype and potentially enhance yield stability (Qiao et al., 2011). However, not all genetic alterations of DEP1 result in positive yield outcomes. For example, the introgression of the qPE9-1 allele, which confers panicle erectness, has been shown to decrease grain yield per plant by 30% in some japonica rice varieties. This reduction is attributed to decreased panicle length, plant height, and 1000-grain weight, highlighting the pleiotropic effects of DEP1 and the need for careful selection of complementary genes in breeding programs (Yi et al., 2011). Furthermore, the combination of DEP1 with other yield-related genes, such as IPA1, has been explored to optimize yield components. Studies have shown that the DEP1 and ipa1 alleles can offset each other’s negative effects, leading to an ideal plant type with improved yield potential (Xu et al., 2014). This synergistic approach underscores the importance of integrating multiple genetic factors to achieve desirable agronomic traits. 3.3 Field results of DEP1 modulation Several studies have demonstrated the impact of DEP1 modulation on rice yield through field trials. For instance, the introduction of the dominant DEP1 allele into various rice cultivars has consistently resulted in increased grain yield due to enhanced panicle architecture. The gain-of-function mutation in DEP1 leads to a higher number of grains per panicle, which directly translates to increased yield (Huang et al., 2009).
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