Ye Meixia, Chen Zhong, Su Xiaoxing, Ji Lexiang, Wang Jia, Liao Weihua, Ma Huandi, An Xinmin
National Engineering Laboratory for Tree Breeding, Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, The Tree and Ornamental Plant Breeding and Biotechnology Laboratory, Beijing Forestry University, Beijing 100083, People's Republic of China.
BMC Genomics. 2014 Jun 14;15(1):475. doi: 10.1186/1471-2164-15-475.
Poplar seed hair is an environmental annoyance in northern China due to its abundance and widespread airborne distribution after maturation. The morphogenesis and molecular mechanisms of its development are not well understood, and little attention has been focused on the dynamics of its development. To better understand the mechanism of poplar seed hair development, paraffin sections were used to examine the initiation and elongation of poplar seed hairs. RNA-seq technology was also employed to provide a comprehensive overview of transcriptional changes that occur during seed hair development.
The placenta at the base of ovary, was identified as the origin of seed hair development, which is in sharp contrast to cotton fibers that originate from epidermal cells of the seed coat. An enlarged cell nucleus in seed hair cells was also observed, which was supported by our gene ontology enrichment analysis. The significant enriched GO term of "endoreduplication" indicated that cycles of endoreduplication, bypassing normal mitosis, is the underlying mechanisms for the maintenance of the uni-cellular structure of seed hairs. By analyzing global changes in the transcriptome, many genes regulating cell cycle, cell elongation, cell well modification were identified. Additionally, in an analysis of differential expression, cellulose synthesis and cell wall biosynthesis-related biological processes were enriched, indicating that this component of fiber structure in poplar seed hairs is consistent with what is found in cotton fibers. Differentially expressed transcription factors exhibited a stage-specific up-regulation. A dramatic down-regulation was also revealed during the mid-to-late stage of poplar seed hair development, which may point to novel mechanisms regulating cell fate determination and cell elongation.
This study revealed the initiation site of poplar seed hairs and also provided a comprehensive overview of transcriptome dynamics during the process of seed hair development. The high level of resolution on dynamic changes in the transcriptome provided in this study may serve as a valuable resource for developing a more complete understanding of this important biological process.
在中国北方，杨树种子毛是一种环境困扰，因为其数量众多，成熟后广泛分布于空气中。其发育的形态发生和分子机制尚未得到充分了解，人们对其发育动态关注较少。为了更好地理解杨树种子毛发育的机制，我们使用石蜡切片来研究杨树种子毛的起始和伸长。还采用了RNA测序技术，以全面概述种子毛发育过程中发生的转录变化。
子房基部的胎座被确定为种子毛发育的起源，这与源自种皮表皮细胞的棉纤维形成鲜明对比。我们还观察到种子毛细胞中的细胞核增大，这得到了基因本体富集分析的支持。“核内复制”这一显著富集的基因本体术语表明，绕过正常有丝分裂的核内复制循环是维持种子毛单细胞结构的潜在机制。通过分析转录组的全局变化，鉴定出许多调节细胞周期、细胞伸长和细胞壁修饰的基因。此外，在差异表达分析中，纤维素合成和细胞壁生物合成相关的生物学过程得到富集，表明杨树种子毛纤维结构的这一组成部分与棉纤维中的情况一致。差异表达的转录因子表现出阶段特异性上调。在杨树种子毛发育的中后期也发现了显著下调，这可能指向调节细胞命运决定和细胞伸长的新机制。
本研究揭示了杨树种子毛的起始位点，并全面概述了种子毛发育过程中的转录组动态。本研究提供的转录组动态变化的高分辨率信息，可能是更全面了解这一重要生物学过程的宝贵资源。
