Promoter variations in a homeobox gene, BnA10.LMI1, determine lobed leaves in rapeseed (Brassica napus L.)

Abstract

BnA10.LMI1 positively regulates the development of leaf lobes in Brassica napus, and cis-regulatory divergences cause the different allele effects. Leaf shape is an important agronomic trait, and large variations in this trait exist within the Brassica germplasm. The lobed leaf is a unique morphological characteristic for Brassica improvement. Nevertheless, the molecular basis of leaf lobing in Brassica is poorly understood. Here, we show that an incompletely dominant locus, BnLLA10, is responsible for the lobed-leaf shape in rapeseed. A LATE MERISTEM IDENTITY1 (LMI1)-like gene (BnA10.LMI1) encoding an HD-Zip I transcription factor is the causal gene underlying the BnLLA10 locus. Sequence analysis of parental alleles revealed no sequence variations in the coding sequences, whereas abundant variations were identified in the regulatory region. Consistent with this finding, the expression levels of BnLMI1 were substantially elevated in the lobed-leaf parent compared with its near-isogenic line. The knockout mutations of BnA10.LMI1 gene were induced using the CRISPR/Cas9 system in both HY (the lobed-leaf parent) and J9707 (serrated leaf) genetic backgrounds. BnA10.LMI1 null mutations in the HY background were sufficient to produce unlobed leaves, whereas null mutations in the J9707 background showed no obvious changes in leaf shape compared with the control. Collectively, our results indicate that BnA10.LMI1 positively regulates the development of leaf lobes in B. napus, with cis-regulatory divergences causing the different allelic effects, providing new insights into the molecular mechanism of leaf lobe formation in Brassica crops.

Targeted mutagenesis of BnTT8 homologs controls yellow seed coat development for effective oil production in Brassica napus L.

“…In recent years, sequence‐specific nucleases (SSNs) have been demonstrated to be an amazing tool for the improvement of crops via site‐specific genome editing, and CRISPR/Cas9 is considered the most simple and efficient SSN. The CRISPR/Cas9 system has been effectively utilized in rapeseed to produce the targeted mutagenesis required to improve agronomic traits (Braatz et al , ; Hu et al , ; Li et al , ; Yang et al , ; Yang et al , ; Zhai et al , ; Zheng et al , ).…”

Targeted mutagenesis of EOD3 gene in Brassica napus L. regulates seed production

“…Rapeseed ( Brassica napus L., AACC, 2 n = 38), is an important crop grown all over the world, providing approximately 16% of the entire global edible vegetable oils for human diets as well as high‐quality animal feed proteins and raw materials for industrial processes (Hu et al, 2018; S. U. Khan et al, 2019). It resulted from a recent allopolyploidy between ancestors of Brassica rapa (2 n = 20, AA) and Brassica oleracea (2 n = 18, CC).…”

“…It has been used for genome editing in major crops (Ahmar et al, 2020; M. H. U. Khan et al, 2018). It has been efficiently utilized in rapeseed to produce the targeted mutagenesis required to improve agronomic traits, including multilocular silique, plant height and architecture, pod shatter resistance, yellow seeds, fatty acid composition, and disease resistance (Braatz et al, 2017; Hu et al, 2018; Huang et al, 2020; C. Li et al, 2018; Pröbsting et al, 2020; H. Yang, Wu, Tang, Liu, & Dai, 2017; Y. Yang et al, 2018; Zhai et al, 2019, 2020; Zheng et al, 2019).…”

Fine Mapping of a Locus Underlying the Ectopic Blade-Like Outgrowths on Leaf and Screening Its Candidate Genes in Rapeseed (Brassica napus L.)

“…Leaves are photosynthetic organs of plants, and they play a vital role in photosynthate accumulation, gas exchange, nutrient distribution, and water transport (Tsukaya, 2006;Hu et al, 2018). Leaf shape is a crucial character, and it is very important to influence the success of plants and has been refined through the evolution (Tsukaya, 2005).…”

“…It can significantly affect yield and quality of crops (Zhu et al, 2016). In addition, special leaf morphology, like the functional significance of lobed leaves in rapeseed (Brassica napus L.), which is one of the most important oil crops globally, has been identified with potential advantages for high-density planting, which benefits mechanized harvesting in mechanical production, as well as hybrid production (Ni et al, 2017;Hu et al, 2018).…”