磷元素作为植物所必需的三大营养元素（氮、磷、钾）之一，在各种生命过程中发挥着重要作用。在农业生产中一般通过施加磷肥来增加土壤中的磷含量，然而磷肥的过度施用不仅导致农业生产成本的升高，而且造成严重的土壤及水体污染。此外，作为磷肥主要来源的磷矿为不可再生资源，其在几十年内行将枯竭。因此，通过分子生物学手段改造植物使其具有高效的磷吸收转运和利用能力将是解决这一系列问题的最佳手段。

中国科学院遗传与发育生物学研究所基因组学国家重点实验室储成才课题组通过图位克隆方法，从重要农作物水稻中分离出磷饥饿应答反应的关键调控基因 LEAF TIP NECROSIS 1(LTN1)。该基因的突变导致水稻叶片中大量积累无机磷，进而导致磷毒害的表型。研究表明，LTN1能够影响磷转运子的表达进而调控了磷的吸收与转运。同时，LTN1还参与调控磷饥饿环境下的根形态改变、酸性磷酸酶和核糖核酸酶活性调控、脂类成份转变、氮及金属元素吸收调控等多种磷饥饿应答反应。该研究进一步证明，LTN1是microRNA399下游的靶基因，microRNA399通过介导其转录本的降解在转录后水平对其进行负调控。

该项研究鉴定出的调控水稻中磷饥饿应答反应关键基因LTN1，不仅为进一步揭示水稻乃至其他作物中磷饥饿应答反应的分子机制奠定了基础，也为人们创制磷高效吸收利用的转基因作物提供了新思路。这项成果已于2月11日在国际杂志《植物生理学》（Plant Physiology）上在线发表（）。

论文摘要：

Although phosphate (Pi) starvation signaling is well studied in Arabidopsis, it is still largely unknown in rice. In this work, a rice leaf tip necrosis1 (ltn1) mutant was identified and characterized. Map-based cloning identified LTN1 as LOC_Os05g48390, the putative ortholog of Arabidopsis PHO2, which plays important roles in Pi starvation signaling. Analysis of transgenic plants harboring a LTN1 promoter:: GUS construct revealed that LTN1 was preferentially expressed in vascular tissues. The ltn1 mutant exhibited increased Pi uptake and translocation, which lead to Pi over-accumulation in shoots. In association with enhanced Pi uptake and transport, some Pi transporters were up-regulated in the ltn1 mutant in the presence of sufficient Pi. Furthermore, the elongation of primary and adventitious roots was enhanced in the ltn1 mutant under Pi starvation, suggesting that LTN1 is involved in Pi-dependent root architecture alteration. Under Pi sufficient conditions, typical Pi starvation responses such as stimulation of phosphatase and ribonuclease activities, lipid composition alteration, nitrogen assimilation repression, and increased metal uptake were also activated in ltn1. Moreover, analysis of OsmiR399 over-expressing plants showed that LTN1 was down-regulated by OsmiR399. Our results strongly indicate that LTN1 is a crucial Pi starvation signaling component downstream of miR399 involved in the regulation of multiple Pi starvation responses in rice.

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