Abstract
Plant architecture involves important agronomic traits affecting crop yield, resistance to lodging, and fitness for mechanical harvesting in Brassica napus. Breeding high-yield varieties with plant architecture suitable for mechanical harvesting is the main goal of rapeseed breeders. Here, we report an accession of B. napus (4942C-5), which has a dwarf and compact plant architecture in contrast to cultivated varieties. A BC8 population was constructed by crossing a normal plant architecture line, 8008, with the recurrent parent 4942C-5. To investigate the molecular mechanisms underlying plant architecture, we performed phytohormone profiling, bulk segregant analysis sequencing (BSA-Seq), and RNA sequencing (RNA-Seq) in BC8 plants with contrasting plant architecture. Genetic analysis indicated the plant architecture traits of 4942C-5 were recessive traits controlled by multiple genes. The content of auxin (IAA), gibberellin (GA), and abscisic acid (ABA) differed significantly between plants with contrasting plant architecture in the BC8 population. Based on BSA-Seq analysis, we identified five candidate intervals on chromosome A01, namely those of 0 to 6.33 Mb, 6.45 to 6.48 Mb, 6.51 to 6.53 Mb, 6.77 to 6.79 Mb, and 7 to 7.01 Mb regions. The RNA-Seq analysis revealed a total of 4378 differentially expressed genes (DEGs), of which 2801 were up-regulated and 1577 were down-regulated. There, further analysis showed that genes involved in plant hormone biosynthesis and signal transduction, cell structure, and the phenylpropanoid pathway might play a pivotal role in the morphogenesis of plant architecture. Association analysis of BSA-Seq and RNA-Seq suggested that seven DEGs involved in plant hormone signal transduction and a WUSCHEL-related homeobox (WOX) gene (BnaA01g01910D) might be candidate genes responsible for the dwarf and compact phenotype in 4942C-5. These findings provide a foundation for elucidating the mechanisms underlying rapeseed plant architecture and should contribute to breed new varieties suitable for mechanization.
Highlights
Plant architecture is defined as the three-dimensional organization of plant organs, including plant height, branch or tiller angle, and number, leaf shape, and other organs’ morphology [1,2]
Among the offspring of crosses between 4942C-5 and 8008, we found several lines whose plant architecture was deemed suitable for mechanical harvesting, namely semi-dwarf plant height, narrow branch angle, and short silique layer (Figure S2)
Given the functional analysis of differentially expressed genes (DEGs) and in light of previous studies, we focused on those DEGs related to plant hormone signal transduction to uncover the molecular mechanisms of plant architecture in B. napus
Summary
Plant architecture is defined as the three-dimensional organization of plant organs, including plant height, branch or tiller angle, and number, leaf shape, and other organs’ morphology [1,2]. Plant architecture directly affects the adaptability of species to cultivation, the potential yield of crops, and their suitability to modern agricultural production operations, such as mechanical harvesting. Plant height is recognized as a fundamental trait of plant architecture that affect lodging resistance and crop yield. The optimum plant height, tiller angle, and branch numbers jointly determine photosynthetic efficiency and planting density and the potential biomass yield increase of a crop. Many plant-architecture-related mutants in rice, wheat, maize, and Arabidopsis have been identified and their molecular mechanisms were revealed to assist in breeding new varieties with an ideal plant phenotype [2]
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