A member of the maize isopentenyl transferase gene family, Zea mays isopentenyl transferase 2 (ZmIPT2), encodes a cytokinin biosynthetic enzyme expressed during kernel development
A member of the maize isopentenyl transferase gene family, Zea mays isopentenyl transferase 2 (ZmIPT2), encodes a cytokinin biosynthetic enzyme expressed during kernel development
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DOI：
10.1007/s11103-008-9312-x
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发表时间：
2008-06-01
影响因子：
5.1
通讯作者：
Habben, Jeffrey E.
中科院分区：
文献类型：
--
作者：
Brugiere, Norbert;Humbert, Sabrina;Habben, Jeffrey E.
细胞分裂素（Cytokinins，CKs）是一种植物激素，在植物生长发育过程中起着重要的调节作用，如诱导气孔开放、延缓衰老、抑制生长素诱导的顶端优势、传递氮素有效性信号、质体分化和控制库强度等。在玉米中，CK被认为在正常和不利的环境条件下在建立种子大小和增加结实方面起重要作用，因此影响产量。近年来，异戊烯基转移酶（IPT）基因在植物中的发现为植物CK生物合成途径的研究提供了新的思路。为了增加我们对CKs在玉米发育和库强度中所起作用的理解，我们使用生物信息学方法确定了几个假定的IPT基因。我们将注意力集中在一个基因上，特别是ZmIPT 2，因为它在发育中的籽粒中表达强烈。该基因及其产物的表达覆盖CK水平的变化，在发展中的内核，表明CK生物合成的核心发展的主要作用。我们证明，在授粉后8-10天（DAP）的胚乳，特别是基底转移细胞层（BETL）是ZmIPT 2表达的主要位点，并且这种表达持续在BETL和发育中的胚进入后期的籽粒发育阶段。我们发现，异位表达ZmIPT 2在愈伤组织和植物产生的表型与CK生产过剩。我们还表明，ZmIPT 2优先使用ADP和ATP超过AMP作为底物的二甲基烯丙基二磷酸（DMAPP）IPT活动。ZmIPT 2的表达模式在BETL，胚乳和胚在籽粒发育过程中将讨论的重点建议的作用，CK在确定库强度和粮食生产的作物植物。
Cytokinins (CKs) are plant hormones that regulate a large number of processes associated with plant growth and development such as induction of stomata opening, delayed senescence, suppression of auxin-induced apical dominance, signaling of nitrogen availability, differentiation of plastids and control of sink strength. In maize, CKs are thought to play an important role in establishing seed size and increasing seed set under normal and unfavorable environmental conditions therefore influencing yield. In recent years, the discovery of isopentenyl transferase (IPT) genes in plants has shed light on the CK biosynthesis pathway in plants. In an effort to increase our understanding of the role played by CKs in maize development and sink-strength, we identified several putative IPT genes using a bioinformatics approach. We focused our attention on one gene in particular, ZmIPT2, because of its strong expression in developing kernels. The expression of the gene and its product overlays the change in CK levels in developing kernels suggesting a major role in CK biosynthesis for kernel development. We demonstrate that at 8-10 days after pollination (DAP) the endosperm and especially the basal transfer cell layer (BETL) is a major site of ZmIPT2 expression, and that this expression persists in the BETL and the developing embryo into later kernel development stages. We show that ectopic expression of ZmIPT2 in calli and in planta created phenotypes consistent with CK overproduction. We also show that ZmIPT2 preferentially uses ADP and ATP over AMP as the substrates for dimethylallyl diphosphate (DMAPP) IPT activity. The expression pattern of ZmIPT2 in the BETL, endosperm and embryo during kernel development will be discussed with an emphasis on the suggested role of CKs in determining sink-strength and grain production in crop plants.