水稻株型发育遗传调控网络的解析

Plant architecture is the morphological basis of yield formation and optimizing plant architecture to achieve higher yield is always the main target of rice breeding. A few of important genes controlling plant architecture have been successfully identified in rice, however, their regulatory networks remain largely unknown. Our group has previously cloned three key genes, TAC1, PROG1 and SUP1, affecting rice plant architecture. The aim of the present study is (1) to isolate and functionally characterize novel genes for the plant architecture of rice using both forward and reverse genetics, and to identify their causal regulatory sites and downstream genes; (2) to examine the genetic interaction among genes controlling rice plant architecture and then construct the underlying genetic regulatory network; (3) to mine the allelic spectrum of genes for plant architecture in diverse wild and cultivated rice germplasm through association analysis and then identify the potentially favorable alleles that can be used in the selective breeding of rice. The findings of this project not only sheds light on the regulatory network of rice plant architecture, but also provides a theoretical basis for the molecular breeding of plant architecture and yield-related traits in rice.

株型是产量建成的形态学基础，塑造理想株型将有利于提高水稻单产潜力。近年来已经成功克隆了多个控制水稻株型的重要基因，但是其遗传调控网络尚不清楚。本项目拟在前期克隆水稻株型相关基因TAC1、PROG1和SUP1（PROG1抑制基因）的基础上，通过正向和反向遗传学方法，继续分离、克隆株型发育调控途径中的新基因，验证其功能，鉴定其调控位点和下游调控基因；分析水稻株型相关基因的遗传互作关系，构建株型发育遗传调控网络；采用关联分析方法鉴定株型调控相关基因的功能性位点，明确不同等位基因的遗传效应，从野生稻和栽培稻中挖掘具有应用潜力的优良等位基因。本项目研究结果为解析水稻株型发育遗传调控网络这一重要科学问题提供重要参考，同时还为株型及产量性状的分子改良提供理论基础。

株型是产量形成的形态学与生理学基础，塑造理想株型将有利于提高水稻产量。虽然已经鉴定了多个控制水稻株型的重要基因，但是其遗传调控网络尚不清楚。本项目继续克隆株型发育调控途径中的新基因，构建株型发育遗传调控网络。通过进一步分析PAY1调控水稻株型和产量的机理和LABA1控制芒长及芒刺的发育机理。发现PAY1基因调控生长素的合成以及极性运输能力，进而改变了体内生长素的极性分布，改良株型，增加穗粒数，提高产量。LABA1编码一个细胞分裂素活性酶，通过影响芒原基细胞分裂素的水平，控制芒刺形成和芒的伸长受阻。通过正向遗传学方法，鉴定了TAC3、TAC4、TAC8及HTD12等4个控制株型发育新基因。其中，TAC3突变，使茎基部外侧的生长素含量下降，导致分蘖向重力性降低，分蘖角度增大分蘖角度增大、株型变松散、株高显著下降，穗粒数、千粒重和单株产量均显著下降。TAC8源自野生稻，位于第8染色体，其C端具有转录激活活性，能够显著上调TAC1、PCNA等相关基因的表达。野生稻的TAC8可能特异地在茎基部的远地侧表达，使该部位的细胞伸长变大，茎基部两侧的细胞大小差异减小，分蘖角度增大。htd12源自一个簇生矮秆多分蘖的水稻突变体，位于第12染色体着丝点附近。下调HTD12 的表达，株高降低、分蘖数增加、穂粒数减少；上调HTD12表达，则表现株高增加、分蘖减少、穂粒数增加。HTD12参与类胡萝卜素的合成，该基因突变使类胡萝卜素合成合成受阻，影响独角金内酯（SLs）及油菜素内酯（BR）的合成，从而引起株高、分蘖数等性状的改变。TAC4控制分蘖角度和穗粒数基因，位于第4染色体，下调表达分蘖角度变大，株型都变得松散，穗粒数减少。TAC4蛋白被定位在细胞核，在叶鞘枕和茎秆等输导组织丰富的部位持续高表达，并在叶片、根和幼穗中也有较高表达。通过分析PAY1、TAC3、TAC4、TAC8、HTD12与GROG1和TAC1之间的关系，初步构建了水稻株型遗传调控网络。本项目研究结果不仅为解析水稻株型发育遗传调控网络这一重要科学问题提供重要基础，同时还为株型及产量性状的分子改良提供了重要基因。