Dessection of developmental program in rice

我们已经发现，至少有四个位点（SHL 1和SHL 4）参与水稻茎尖分生组织（SAM）的起始。为了解决SHL基因如何与SAM的维持相关，我们新鉴定了SHL 2的三个弱等位基因shl 2 -6和shl 2 -8，以及SHL 1的一个弱等位基因shl 1 -3。SHL 1和SHL 2基因在SAM的维持中起着重要作用。此外，它们还调节叶原基的发育模式。弱shl等位基因发育出不规则叶序中产生小线状叶的异常幼苗。弱shl等位基因的幼苗表型与sho突变体相似。shl 2 -6 sho 2双突变体表明sho 2在sho 2的上游发挥功能。为了深入研究穗和花的发育机制，我们分析了apo 1突变体的穗和花的异常组织。apo 1在花序轴和枝上的分生组织特性发生了早熟的转化，从而产生顶生花。在apo 1花中，浆片增加，但雄蕊减少。大量雌蕊不定地产生。这些表型表明，APO 1基因在生殖阶段调节分生组织身份的转换时间。为了阐明根形成的程序，我们鉴定了冠状根（不定根）形成缺陷的突变体。有的突变体根原基伸长障碍，有的不能形成根原基。因此，在根的形成中存在许多基因的复杂级联。

We have already revealed that at least four loci (SHL1〜SHL4) are involved in the initiation of shoot apical meristem (SAM) in rice. To address how SHL genes are associated with the maintenance of SAM, we have newly identified three weak alleles, shl2-6〜shl2-8, of SHL2 and one weak allele, shl1-3, of SHL1. It is revealed that SHL1 and SHL2 genes are indispensable for the maintenance of SAM. In addition, they also regulate the developmental pattern of leaf primordia. Weak shl alleles developed abnormal seedlings producing small thread-like leaves in irregular phyllotaxy. The seedling phenotype of weak shl alleles is similar to that of sho mutants. Double mutant of shl2-6 sho2 suggests that SHO2 function upstream of SHO2.For dissecting developmental mechanism of panicle and flower, we have analyzed apo1 mutants showing abnormal organization of panicle and flowers. The apo1 produced terminal flowers due to the precocious transformation of meristem identity in rachis and branches. In apo1 flowers, lodicules were increased but stamens were decreased. A large number of pistils were produced indeterminately. These phenotypes suggest that APO1 gene regulates temporal y the transformation of meristem identity in reproductive phase.To elucidate the program for root formation, we identified mutants defective in crown root (adventitious root) formation. Some mutants have defect in the elongation of root primordia, and the other failed to form root primordia. Thus, there exists a complex cascade of many genes in root formation.