Sato Dai-Suke, Ohmori Yoshihiro, Nagashima Haruka, Toriba Taiyo, Hirano Hiro-Yuki
Department of Biological Sciences, Graduate School of Science, The University of Tokyo.
Genes Genet Syst. 2014;89(2):61-9. doi: 10.1266/ggs.89.61.
The lemma and palea, which enclose the pistil, stamens, and lodicules, are the most conspicuous organs in the rice spikelet. We isolated a mutant line (ng6569) in which the lemma and palea were narrower than those of the wild type, and found that the mutant had a defect in TRIANGULAR HULL1 (TH1), which encodes a nuclear protein with an ALOG domain. Detailed morphological analysis indicated that the th1 mutation caused a reduction in the size of tubercles, which are convex structures on the surface of the lemma and palea. This reduction was more pronounced in the apical region of the lemma than in the basal region, resulting in the formation of a beak-like spikelet. By contrast, the number of tubercle rows and their spatial distribution on the lemma were not affected in the th1 mutant. Thus, the TH1 gene seems to be involved in fine-tuning the morphogenesis of the lemma and palea. In situ hybridization analysis revealed that TH1 was highly expressed in the primordia of the lemma and palea, but only weakly expressed in the primordia of the sterile lemma and rudimentary glume. We then examined the effect of th1 mutation on the lemma-like structure formed in the long sterile lemma/glume1 (g1) and extra glume1 (eg1) mutants. The result showed that the th1 mutation strongly affected the morphology of the extra lemma of eg1, but had no significant effect on the transformed lemma of g1.
包裹雌蕊、雄蕊和浆片的内稃和外稃是水稻小穗中最显著的器官。我们分离出一个突变系（ng6569），其内外稃比野生型窄，并发现该突变体的三角颖壳1（TH1）存在缺陷，TH1编码一种具有ALOG结构域的核蛋白。详细的形态学分析表明，th1突变导致瘤状突起（内外稃表面的凸起结构）尺寸减小。这种减小在稃尖区域比基部区域更明显，导致形成喙状小穗。相比之下，th1突变体中瘤状突起的行数及其在稃上的空间分布不受影响。因此，TH1基因似乎参与了内外稃形态发生的精细调控。原位杂交分析显示，TH1在内外稃原基中高表达，但在不育外稃和退化颖片原基中仅弱表达。然后我们研究了th1突变对长不育颖片/颖壳1（g1）和额外颖壳1（eg1）突变体中形成的类稃结构的影响。结果表明，th1突变强烈影响eg1额外稃的形态，但对g1转化稃没有显著影响。
