A gibberellin-regulated xyloglucan endotransglycosylase gene is expressed in the endosperm cap during tomato seed germination
A gibberellin-regulated xyloglucan endotransglycosylase gene is expressed in the endosperm cap during tomato seed germination
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DOI：
10.1093/jexbot/53.367.215
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发表时间：
2002-02-01
影响因子：
6.9
通讯作者：
Bradford, KJ
中科院分区：
文献类型：
--
作者：
Chen, F;Nonogaki, H;Bradford, KJ
木葡聚糖内糖基转移酶(XETs)修饰木葡聚糖，木葡聚糖是双子叶植物初级细胞壁的主要成分。从番茄萌发过程中分离到一个XET基因(LeXET4)。种子cDNA文库。DNA凝胶印迹分析表明，LeXET4基因在番茄基因组中为单拷贝基因。LeXET4在萌发种子中有较强的表达，在茎中含量较低，在根、叶和花组织中未检测到。在萌发过程中，种子在吸胀12h内检测到LeXET4mRNA，并在24h达到最大丰度，组织印迹显示LeXET4mRNA仅定位于胚乳帽区。在转基因番茄种子中，LeXET4的表达依赖于外源赤霉素(GA)，而种子萌发抑制物脱落酸对野生型种子中LeXET4的表达没有影响。LeXET4mRNA在胚根出现后消失，尽管侧生胚乳细胞壁继续退化。LeXET4基因表达的时间、空间和激素调控模式表明，XET在调节番茄种子萌发的关键过程--胚乳帽的弱化中起作用。
Xyloglucan endotransglycosylases (XETs) modify xyloglucans, major components of primary cell walls in dicots. A cDNA encoding an XET (LeXET4) was isolated from a germinating tomato (Lycopersicon esculentum Mill.) seed cDNA library. DNA gel blot analysis showed that LeXET4 is a single-copy gene in the tomato genome. LeXET4 mRNA was strongly expressed in germinating seeds, was much less abundant in stems, and was not detected in roots, leaves or flower tissues. During germination, LeXET4 mRNA was detected in seeds within 12 h of imbibition with maximum mRNA abundance at 24 h. Tissue prints showed that LeXET4 mRNA was localized exclusively to the endosperm cap region. Expression of LeXET4 was dependent on exogenous gibberellin (GA) in GA-deficient (gib-1 mutant) tomato seeds, while abscisic acid, a seed germination inhibitor, had no effect on LeXET4 mRNA expression in wild-type seeds. LeXET4 mRNA disappeared after radicle emergence, even though degradation of the lateral endosperm cell walls continued. The temporal, spatial and hormonal regulation pattern of LeXET4 gene expression suggests that XET has a role in endosperm cap weakening, a key process regulating tomato seed germination.