Plant Gene and Trait 2024, Vol.15, No.2, 73-84 http://genbreedpublisher.com/index.php/pgt 76 In another study, the dense and erect panicle 3 (DEP3) mutant, derived from the Oryza sativa ssp. japonica cultivar Hwacheong, exhibited a similar phenotype with erect panicles and increased grain number per panicle. The DEP3 gene, identified as a patatin-like phospholipase A2 (PLA2) superfamily domain-containing protein, plays a significant role in the formation of vascular bundles, contributing to the dense and erect panicle phenotype. This mutation provides another valuable resource for rice breeding programs aimed at improving yield (Qiao et al., 2011). Furthermore, the CLUSTERED PRIMARY BRANCH 1 (CPB1) gene, a new allele of DWARF11 (D11), has been shown to control panicle architecture and seed size. Overexpression of CPB1/D11 in rice plants resulted in larger seed size and enhanced grain yield without negatively affecting other agronomic traits. This demonstrates the potential of manipulating CPB1/D11 expression to improve rice yield through genetic modulation (Wu et al., 2016). The Short Panicle 3 (SP3) gene, encoding a DNA binding with one finger (Dof) transcriptional activator, also influences panicle architecture by modulating cytokinin homeostasis. Knockdown mutations in SP3 lead to smaller panicles with fewer branches and spikelets, highlighting the importance of SP3 in regulating panicle development and grain yield (Huang et al., 2019). 4 Case Studies: DEP1 and Rice Yield Enhancement 4.1 Analysis of DEP1 gene manipulation experiments Due to the significant impact of the DEP1 gene on panicle architecture, it has become a focal point for enhancing rice yield. The dominant allele at the DEP1 locus is a gain-of-function mutation that enhances meristematic activity, leading to a reduced length of the inflorescence internode and an increased number of grains per panicle, thereby boosting rice yield. This allele is prevalent in many high-yielding Chinese rice varieties and is a relatively recent addition to the cultivated rice gene pool (Huang et al., 2009). Additionally, the use of CRISPR/Cas9 gene editing technology to edit the DEP1 locus has been shown to improve canopy structure, allowing more light to reach the leaves below the panicle, thereby increasing biomass and yield under low-fertilizer conditions (Fei et al., 2019). Huang et al. (2018) studied the use of CRISPR/Cas9 technology to edit the DEP1 gene, resulting in multiple mutants that exhibited an increased number of grains per panicle and overall yield improvement (Huang et al., 2018). Zhao et al. (2019) demonstrated that genome editing-induced mutagenesis can develop superior DEP1 gene alleles (Figure 1), further enhancing grain yield under controlled conditions. Figure 1 Generation of DEP1overexpressed plants (Adopted from Zhao et al., 2019) Image caption: (A) The construct of the plasmid containing the CaMV 35S promoter (35S), DEP1 and the terminator (Tnos) between the right (RB) and the left (LB) borders of the T-DNA. The hygromycin resistance gene (HYG) was located between the LB and the 35S promoter. (B) Identification of positive transgenic plants in T0 generation by PCR. (C) Panicle architecture for wildtype and transgenic T0 plants. (D) Expression levels of DEP1 in transgenic T0 plants. Expression levels relative to wildtype plants set to be one. Data shown as means ± SD (n = 3). (E) Identification of copy numbers in transgenic T0 plants and homozygote in transgenic T1 plants by quantitative real-time PCR (Adopted from Zhao et al., 2019)
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