缺磷是制约我国玉米中低产地区产量持续提高的主要因素之一，但是玉米如何响应低磷的深层分子和遗传机制并不清晰。我们研究发现，缺磷强烈诱导玉米根中CCD8基因（类胡萝卜素裂解双加氧酶8）可变剪接，至少产生CCD8-1、CCD8-2、CCD8-3（从长到短）三种转录本；其中，CCD8-1表达上调100多倍。CCD8-1和CCD8-2能够对拟南芥同源基因突变体的多分枝表型进行互补；而对照条件的转录本CCD8-3在N端缺失三个β折叠，不能互补拟南芥同源基因突变体的多分枝表型。种间比较研究表明，CCD8的这种低磷可变剪接响应在栽培玉米和野生玉米之间是保守的。鉴于此，本申请将利用分子生物学、生物化学、和表观遗传学等方法深入研究玉米CCD8基因响应低磷的可变剪接调控、蛋白定位、蛋白相互作用、基因调控网络、可变剪接体的生物学功能、以及可变剪接的表观遗传调控机制，为玉米磷高效品种选育和持续增产提供新的理论支撑。

Phosphorus insufficiency is a major limiting factor for maize production in medium- or low-yield areas in China; however, it remains unclear how maize plants respond to low phosphorus supplies at the molecular and genetic levels. We found that phosphorus deficiency strongly induces alternative splicing of ZmCCD8 (carotenoid cleavage dioxygenase 8) with at least three transcripts: CCD8_1、CCD8_2、CCD8_3 according to their length. CCD8-1 is up-regulated more than 100 times by phosphorus insufficiency. CCD8_1 and CCD8_2 are able to complement branching phenotype of max4, the knockout mutant of Arabidopsis CCD8 homologue, while CCD8_3, the dominant transcript under control, fails to do so probably due to lack of three β-sheets. Multiple transcripts of CCD8 are found in both maize and teosintes, indicating alternative splicing of CCD8 is conserved among these closely related species. Taking advantage of molecular, biochemical, epigenetic approaches, we specifically investigate alternative splicing of CCD8, protein localization, protein-protein interaction, biological functions of alternative transcripts, and epigenetic regulation of alternative splicing. This proposal investigates molecular and genetic mechanisms of how maize responds to low phosphorus, which lays theoretic foundation for phosphorus efficient maize breeding and continuous yield increase in maize production.