Asymmetric transcriptomic signatures between the cob and florets in the maize ear under optimal- and low-nitrogen conditions at silking, and functional characterization of amino acid transporters ZmAAP4 and ZmVAAT3.
Asymmetric transcriptomic signatures between the cob and florets in the maize ear under optimal- and low-nitrogen conditions at silking, and functional characterization of amino acid transporters ZmAAP4 and ZmVAAT3.
复制标题
在最佳氮和低氮条件下吐丝时玉米穗轴和小花之间的不对称转录组特征，以及氨基酸转运蛋白 ZmAAP4 和 ZmVAAT3 的功能表征。
DOI：
10.1093/jxb/erv315
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发表时间：
2015-10
影响因子：
6.9
通讯作者：
Li X
中科院分区：
文献类型：
--
作者：
Pan X;Hasan MM;Li Y;Liao C;Zheng H;Liu R;Li X
我们在最佳氮和低氮条件下对玉米芯及其外围小花进行了转录组解剖，并进行了氨基酸转运蛋白 ZmAAP4 和 ZmVAAT3 的功能表征。玉米穗轴和小花的协调运作保证了谷物的产量。穗轴对于谷物发育的碳分配和同化氮 (N) 供应至关重要。然而，穗轴和外周小花的分子识别、介导氮同化物易位的基因特征以及这两种组织对低氮（LN）的反应仍然难以捉摸。对田间吐丝的玉米杂交种的穗部进行转录分析，发现玉米穗轴和小花之间存在 1864 个差异表达基因，其中 1314 个基因在玉米穗中上调，550 个基因在小花中上调。穗轴的特点是参与碳/氮运输和代谢的基因显着富集，这与穗发育过程中穗轴在碳/氮储存和转移中的生理作用一致。小花的特点是激素信号成分和发育相关基因的富集。接下来我们检查了穗轴和小花对液氮胁迫的反应。 LN 导致穗轴中 588 个基因的差异表达，而小花中仅 195 个基因的差异表达，表明穗轴在转录水平上主导了穗对 LN 的反应。液氮引起了玉米穗轴和/或小花基因表达方面的全面改变，例如碳/氮代谢或分配、激素信号传导和蛋白质磷酸化。十四个对 LN 特异性响应的基因为 N 高效玉米育种提供了潜在的分子标记。我们进一步对两种新鉴定的广谱氨基酸转运蛋白 ZmAAP4 和 ZmVAAT3 进行了功能表征，它们在穗轴和小花中显示出不同的表达模式，并在耳朵中的氨基-N 动员中发挥潜在的重要作用。虽然这两种蛋白质都可以将各种氨基酸转运到酵母或拟南芥细胞中，但 ZmAAP4 在转运 22 种检查氨基酸中的 7 种方面似乎比 ZmVAAT3 具有更高的效率。
We performed transcriptomic dissection of the maize cob and its peripheral florets under optimal- and low-nitrogen conditions at silking and functional characterization of amino acid transporters ZmAAP4 and ZmVAAT3. Coordinated functioning of the cob and florets of the maize ear confers grain yield. The cob is critical for carbon partitioning and assimilated nitrogen (N) supply for grain development. However, molecular recognition of the cob and peripheral florets, characterization of genes mediating translocation of N assimilates, and responses of these two tissues to low N (LN) remain elusive. Transcriptional profiling of the ear of a maize hybrid at silking in the field revealed 1864 differentially expressed genes between the cob and florets, with 1314 genes up-regulated in the cob and 550 genes up-regulated in florets. The cob was characterized by striking enrichment of genes that are involved in carbon/N transport and metabolism, consistent with the physiological role of the cob in carbon/N storage and transfer during ear development. The florets were characterized by enrichment of hormone signalling components and development related genes. We next examined the response of the cob and florets to LN stress. LN caused differential expression of 588 genes in the cob and only 195 genes in the florets, indicating that the cob dominated the response of the ear to LN at the transcriptional level. LN caused comprehensive alterations such as carbon/N metabolism or partitioning, hormone signalling and protein phosphorylation in terms of gene expression in the cob and/or florets. Fourteen genes responsive specifically to LN provided potential molecular markers for N-efficient maize breeding. We further functionally characterized two newly identified broad-spectrum amino acid transporters, ZmAAP4 and ZmVAAT3, that showed distinct expression patterns in the cob and florets and potentially important roles in amino-N mobilization in the ear. While both proteins could transport various amino acids into yeast or Arabidopsis cells, ZmAAP4 appeared to have higher efficiencies than ZmVAAT3 in transporting seven out of 22 examined amino acids.