AUTHOR=Yu Kaidi , Li Huailin , Wu Xiaolong , Amoo Olalekan , He Hanzi , Fan Chuchuan , Zhou Yongming 

TITLE=Targeted mutagenesis of BnaSTM leads to abnormal shoot apex development and cotyledon petiole fusion at the seedling stage in Brassica napus L.

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1042430

DOI=10.3389/fpls.2023.1042430

ISSN=1664-462X

ABSTRACT=<p>The Arabidopsis homeodomain transcription factor <italic>SHOOT MERISTEMLESS</italic> (<italic>STM</italic>) is crucial for shoot apical meristem (SAM) function, which cooperates with <italic>CLAVATA3</italic> (<italic>CLV3</italic>)<italic>/WUSCHEL</italic> (<italic>WUS</italic>) feedback regulation loops to maintain the homeostasis of stem cells in SAM. <italic>STM</italic> also interacts with the boundary genes to regulate the tissue boundary formation. However, there are still few studies on the function of <italic>STM</italic> in <italic>Brassica napus</italic>, an important oil crop. There are two homologs of <italic>STM</italic> in <italic>B. napus</italic> (<italic>BnaA09g13310D</italic> and <italic>BnaC09g13580D</italic>). In the present study, CRISPR/Cas9 technology was employed to create the stable site-directed single and double mutants of the <italic>BnaSTM</italic> genes in <italic>B. napus.</italic> The absence of SAM could be observed only in the <italic>BnaSTM</italic> double mutants at the mature embryo of seed, indicating that the redundant roles of <italic>BnaA09.STM</italic> and <italic>BnaC09.STM</italic> are vital for regulating SAM development. However, different from Arabidopsis, the SAM gradually recovered on the third day after seed germination in <italic>Bnastm</italic> double mutants, resulting in delayed true leaves development but normal late vegetative and reproductive growth in <italic>B. napus</italic>. The <italic>Bnastm</italic> double mutant displayed a fused cotyledon petiole phenotype at the seedling stage, which was similar but not identical to the <italic>Atstm</italic> in Arabidopsis. Further, transcriptome analysis showed that targeted mutation of <italic>BnaSTM</italic> caused significant changes for genes involved in the SAM boundary formation (<italic>CUC2</italic>, <italic>CUC3</italic>, <italic>LBDs</italic>). In addition, <italic>Bnastm</italic> also caused significant changes of a sets of genes related to organogenesis. Our findings reveal that the <italic>BnaSTM</italic> plays an important yet distinct role during SAM maintenance as compared to Arabidopsis.</p>