DataSheet_1_Evolution of the Cell Wall Gene Families of Grasses.pdf

Grasses and related commelinid monocot species synthesize cell walls distinct in composition from other angiosperm species. With few exceptions, the genomes of all angiosperms contain the genes that encode the enzymes for synthesis of all cell-wall polysaccharide, phenylpropanoid, and protein constituents known in vascular plants. RNA-seq analysis of transcripts expressed during development of the upper and lower internodes of maize (Zea mays) stem captured the expression of cell-wall-related genes associated with primary or secondary wall formation. High levels of transcript abundances were not confined to genes associated with the distinct walls of grasses but also of those associated with xyloglucan and pectin synthesis. Combined with proteomics data to confirm that expressed genes are translated, we propose that the distinctive cell-wall composition of grasses results from sorting downstream from their sites of synthesis in the Golgi apparatus and hydrolysis of the uncharacteristic polysaccharides and not from differential expression of synthases of grass-specific polysaccharides.

草本植物及相关鸭跖草类单子叶植物(commelinid monocot)所合成的细胞壁，其组成与其他被子植物(angiosperm)存在显著差异。除极少数例外外，所有被子植物的基因组均含有编码维管植物(vascular plant)已知的所有细胞壁多糖、苯丙烷类及蛋白质组分合成所需酶类的基因。本研究通过对玉米(Zea mays)茎秆上下节间发育过程中表达的转录本进行RNA测序(RNA-seq)分析，捕获到了与初生壁或次生壁形成相关的细胞壁相关基因的表达情况。高转录本丰度不仅局限于与草本植物特异性细胞壁相关的基因，还涵盖了与木葡聚糖(xyloglucan)及果胶(pectin)合成相关的基因。结合用于验证表达基因可被翻译的蛋白质组学(proteomics)数据，本研究提出：草本植物细胞壁组成的独特性，并非源于草类特异性多糖合酶的差异表达，而是源于在高尔基体(Golgi apparatus)合成位点下游对多糖的分选过程，以及对非典型多糖的水解作用。