The genome dynamics and function in higher plants

在I. nil、I. purpurea和I. triccolor中，自发的品红、粉红色和紫红色突变体分别开出红色的花，而它们的野生型花开出蓝色或深紫色的花。我们已经确定这些突变体在编码类黄酮3′-羟化酶的f3′h基因中携带点突变或转座子插入，该酶介导花青素色素生物合成中柚皮素和脱氢山酚b环3′位置的羟基化。野生型的红紫色花蕾变成蓝色的开放花，花色的变化与花表皮细胞液泡pH值的升高有关。在缺乏液泡Na+/H+反转运体NHX1基因的突变体中，液泡碱化只发生部分，红紫色的芽变成紫色的开放花。我们发现了一个新的液泡Na+/H+反转运基因NHX2，该基因是在缺乏NHX1活性的情况下，通过部分增加液泡pH值将红紫色芽转化为紫色开放花的基因之一。花呈红棕色或紫灰色的暗色突变体被发现缺乏一种用于花青素生物合成的新型糖基化酶，即UDP-glucose: anthocyanidin 3-O-glucoside-2 ' -O-glucosyltransferase (3GGT)，该酶介导花青素3- o - gluco苷的糖基化，生成3- o - sopho苷。所有被检测的暗突变体都在3GGT基因的相同位置插入4，这些插入引起移码突变。通过称为基因靶向的同源重组修饰基因是表征基因功能的最直接方法，我们已经成功地利用强正负选择修饰了水稻Waxy基因的基因组序列。我们还发现了一个新的水稻DNA转座子nart，它可以用于水稻的基因标记。

The spontaneous magenta, pink and fuchsia mutants in I. nil, I. purpurea and I. tricolor exhibit reddish flowers, respectively, while their wild-type flowers display blue or dark purple flowers. We have identified that these mutants carry either point mutations or transposon insertions within the F3'H gene encoding flavonoid 3'-hydroxylase that mediates hydroxylation of the 3' position of the B-ring of naringenin and dehydrokaempferol in anthocyanin pigment biosynthesis. The reddish-purple buds of the wild-type I. nil change into blue open flowers, and the shift in the flower coloration correlates with an increase in the vacuolar pH of the flower epidermal cell. In the mutant deficient in the NHX1 gene for the vacuolar Na+/H+ antiporter, the vacuolar alkalization occurs only partially, and reddish-purple buds become purple open flowers. We have identified a novel vacuolar Na+/H+ antiporter gene NHX2, which is one of the genes responsible for converting reddish-purple buds into purple open flowers by partially increasing vacuolar pH in the absence of the NHX1 activity. The dusky mutants of I. nil displaying reddish-brown or purplish-gray flowers were found to be deficient in a novel glycosylation enzyme for anthocyanin biosynthesis, UDP-glucose : anthocyanidin 3-O-glucoside-2"-O-glucosyltransferase (3GGT), which mediates the glucosylation of anthocyanidin 3-O-glucosides to yield 3-O-sophorosides. All of the dusky mutants examined were shown to carry 4 by insertions at the identical position in the 3GGT gene, and the insertions caused frameshift mutations.Modification of genes through homologousrecombination termed gene targeting is the most direct method to characterize gene function, and we have succeeded in modifying the rice genomic sequence of the Waxy gene reproducibly by using a strong positive-negative selection. We also identified a novel rice DNA transposon, nDart, which can be used for gene tagging in rice.