Transcriptome analysis of the irregular shape of shoot apical meristem in dt (dou tou) mutant of Brassica napus L.
Molecular Breeding
March 2019, 39:39 | Cite as
Transcriptome analysis of the irregular shape of shoot apical meristem in dt (dou tou) mutant of Brassica napus L.
AuthorsAuthors and affiliations
Ke-Ming ZhuShuo XuKai-Xia LiSheng ChenSundus ZafarWei CaoZheng WangLi-Na DingYan-Hua YangYao-Ming LiXiao-Li Tan
Open Access
Article
First Online: 22 February 2019
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Abstract
Rapeseed (Brassica napus L.) is an important oil crop in the world. In order to fulfill the requirement of mechanized harvesting and raised production, it is highly desirable to gain a better understanding of the regulatory networks controlling the main agronomic traits of this crop. In this study, we obtained a natural mutant of rapeseed with more main stems named as dt (duo tou, meaning more main stems in Chinese). The dt mutant exhibits abnormal differentiation of stems, increased leaves, and decreased plant height. Phenotype and tissue section analysis showed that abnormal development of the shoot apical meristem (SAM) led to the dt phenotype. Genes that participated in SAM activity maintenance, cytokinin biosynthesis, and signal transduction displayed greatly variation at transcriptional level, which was associated with the high level of cytokinin in the dt mutant. These results provide desirable material for improving the breeding and production of Brassica napus.
KeywordsBrassica napus Shoot apical meristem (SAM) Cytokinin RNA sequencing
Ke-Ming Zhu and Shuo Xu contributed equally to this work.
Electronic supplementary material
The online version of this article ( https://doi.org/10.1007/s11032-019-0943-1) contains supplementary material, which is available to authorized users.
Introduction
Rapeseed (Brassica napus L.) is an important oil crop in the world, which is a major resource of edible oil and industrial raw material. To improve the production of rapeseed, great efforts have been made recently to elucidate the molecular mechanisms underlying its important agronomic traits, such as plant height, branch number, and silique number which contribute to rapeseed yields (Chen et al. 2007; Tan et al. 2015; Lu et al. 2017).
Stems and branches are the key yield-related traits, which are differentiated from shoot meristem. The ability of the plant continuously generates new tissues depends on the undifferentiated stem cells activity (Aichinger et al. 2012; Sablowski 2007). After early embryo formation, the shoot begins to form a group of stem cells with a constantly divided capacity. With the onset of seed germination, contributions from stem cells gradually differentiate to form the shoot and root apical meristem (SAM, RAM, respectively). The SAM generates aerial organs throughout the lifespan of higher plants, such as stems, leaves, and flowers (Aichinger et al. 2012; Barton 2010; Stahl and Simon 2005). The meristem must maintain a balance between stem cell niches updating and peripheral organ initiation in order to fulfill this function. In the process of differentiation, the morphological structure, physiological status, and endogenous hormonal content of the SAM undergo substantial change (Chickarmane et al. 2012). These changes represent the periodical characteristics of SAM in different development stages, which were selected as important indicators in this process.
The SAM generates branches and leaves during the vegetative developmental stage. During the reproductive developmental stage, flowers are the main products, which are generated from the floral meristem (Ha et al. 2010). Regardless of the developmental stage, it is important to keep the homeostasis between the stem cell activity maintenance and organ differentiation; this employs a complicated signal network (Ha et al. 2010). SAM stem cell activity is regulated by a feedback loop consisted of WUSCHEL (WUS), CLAVAT3 (CLV3), and related genes (Schoof et al. 2000). In the Arabidopsis SAM, WUS is a key regulator of shoot stem cell maintenance. Mutation of WUS results in the disruption of stem cell formation and meristem development termination (Ikeda et al. 2009; Mayer et al. 1998). Ectopic expression of WUS is also known to be sufficient to induce organ primordium formation and stem cell activity in root tissues (Gallois et al. 2004). CLV3 belongs to the CLV3/ESR protein family and demonstrates an expression domain coincident with SAM stem cell distribution and is the only known molecular marker of these cells (Fletcher et al. 1999). In SAM, the expression of WUS is sufficient to activate the transcription of CLV3 (Leibfried et al. 2005), meanwhile, the activated CLV3 could conversely suppress the expression of WUS through two parallel receptor systems which consist of CLAVATA1 (CLV1) and CLAVATA2 (CLV2) (Brand et al. 2000; Clark et al. 1997; Jeong et al. 1999; Ogawa et al. 2008). Other genes also make significant contributions to the establishment of the SAM shape. In Arabidopsis, SHOOT MERISTEM LESS (STM) facilitates stem cell divi (...truncated)