水稻顶端小穗退化是重要的农艺性状，它引起颖花数减少，造成产量损失。为进一步理解其分子机制，我们从组织培养后代中得到1个隐性穗顶部退化突变体tutou2。利用图位克隆将候选基因定位在第10染色体长臂约75kb区间内。测序发现,在该区域内突变体基因LOC_Os10g31910的第2外显子第941位碱基发生了A→T碱基变化，导致编码氨基酸由异亮氨酸变为苯丙氨酸。互补实验能够使tutou2突变体的表型恢复正常，敲除LOC_Os10g31910也能够获得tutou2突变体同样的表型。这说明：LOC_Os10g31910是引起突变体tutou2穗顶部退化的基因TUTOU2。尽管TUTOU2很可能与已报道的叶片早衰基因DEL1等位，但突变体del1和tutou2之间的表型差异说明DEL1/TUTOU2同时在水稻叶片和穗发育中发挥作用，这在目前还没有充分研究过。

Plant cell walls constitute the skeletal structures of plant bodies, and thus confer lodging resistance for grain crops.  While the basic cell wall synthesis machinery is relatively well established now, our understanding of how the process is regulated remains limited and fragmented.  In this study, we report the identification and characterization of the novel rice (Oryza sativa L.) brittle culm16 (brittle node; bc16) mutant.  The brittle node phenotype of the bc16 mutant appears exclusively at nodes, and resembles the previously reported bc5 mutant.  Combined histochemical staining and electron microscopy assays revealed that in the bc16 mutant, the secondary cell wall formation and thickening of node sclerenchyma tissues are seriously affected after heading.  Furthermore, cell wall composition assays revealed that the bc16 mutation led to a significant reduction in cellulose and lignin contents.  Using a map-based cloning approach, the bc16 locus is mapped to an approximately 1.7-Mb region of chromosome 4.  Together, our findings strengthen evidence for discretely spatial differences in the secondary cell wall formation within plant bodies.

Understanding the genetic mechanism underlying folate biosynthesis and accumulation in rice would be beneficial for breeding high folate content varieties as a cost-effective approach to addressing widespread folate deficiency in developing countries. In this study, the inheritance of rice grain folate content was investigated in the Lemont/Teqing recombinant inbred lines and the Koshihikari/Kasalath//Koshihikari backcross inbred lines. 264 F12 recombinant inbred lines (RILs) and 182 BC1F10 backcross inbred lines (BILs) with their parents planted in randomized complete blocks with two replicates in 2010, and RILs harvested in 2008 were used for QTL detection using inclusive composite interval mapping (ICIM) method. In the RIL population, two QTLs, denoted by qQTF-3-1 and qQTF-3-2 (QTF, quantitative total folate), explaining 7.8% and 11.1-15.8% of the folate content variation were detected in one or two years, respectively. In the BIL population, a QTL, denoted by qQTF-3-3, was detected, explaining 25.3% of the variation in folate content. All the positive alleles for higher folate content were from the high-folate parents, i.e., Teqing and Kasalath. The known putative folate biosynthesis genes do not underlie the QTLs detected in this study and therefore may be novel loci affecting folate content in milled rice. QTLs identified in this study have potential value for marker assisted breeding for high-folate rice variety.