Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, China.
College of Agronomy, Sichuan Agricultural University, Chengdu, Sichuan, China.
BMC Genomics. 2019 Jul 11;20(1):574. doi: 10.1186/s12864-019-5945-1.
Starch biosynthesis in endosperm is a key process influencing grain yield and quality in maize. Although a number of starch biosynthetic genes have been well characterized, the mechanisms by which the expression of these genes is regulated, especially in regard to microRNAs (miRNAs), remain largely unclear.
Sequence data for small RNAs, degradome, and transcriptome of maize endosperm at 15 and 25 d after pollination (DAP) from inbred lines Mo17 and Ji419, which exhibit distinct starch content and starch granule structure, revealed the mediation of starch biosynthetic pathways by miRNAs. Transcriptome analysis of these two lines indicated that 33 of 40 starch biosynthetic genes were differentially expressed, of which 12 were up-regulated in Ji419 at 15 DAP, one was up-regulated in Ji419 at 25 DAP, 14 were up-regulated in Ji419 at both 15 and 25 DAP, one was down-regulated in Ji419 at 15 DAP, two were down-regulated in Ji419 at 25 DAP, and three were up-regulated in Ji419 at 15 DAP and down-regulated in Ji419 at 25 DAP, compared with Mo17. Through combined analyses of small RNA and degradome sequences, 22 differentially expressed miRNAs were identified, including 14 known and eight previously unknown miRNAs that could target 35 genes. Furthermore, a complex co-expression regulatory network was constructed, in which 19 miRNAs could modulate starch biosynthesis in endosperm by tuning the expression of 19 target genes. Moreover, the potential operation of four miRNA-mediated pathways involving transcription factors, miR169a-NF-YA1-GBSSI/SSIIIa and miR169o-GATA9-SSIIIa/SBEIIb, was validated via analyses of expression pattern, transient transformation assays, and transactivation assays.
Our results suggest that miRNAs play a critical role in starch biosynthesis in endosperm, and that miRNA-mediated networks could modulate starch biosynthesis in this tissue. These results have provided important insights into the molecular mechanism of starch biosynthesis in developing maize endosperm.
胚乳中的淀粉生物合成是影响玉米籽粒产量和品质的关键过程。尽管已经对许多淀粉生物合成基因进行了很好的表征，但这些基因的表达调控机制，特别是在 miRNA（microRNA）方面，仍然很大程度上不清楚。
从小麦授粉后 15 和 25 天（DAP）的自交系 Mo17 和 Ji419 的胚乳中小 RNA、降解组和转录组的序列数据表明，miRNAs 介导了淀粉生物合成途径。对这两个系的转录组分析表明，40 个淀粉生物合成基因中有 33 个差异表达，其中 12 个在 Ji419 中在 15 DAP 上调，1 个在 Ji419 中在 25 DAP 上调，14 个在 Ji419 中在 15 和 25 DAP 上调，1 个在 Ji419 中在 15 DAP 下调，2 个在 Ji419 中在 25 DAP 下调，3 个在 Ji419 中在 15 DAP 上调，在 Ji419 中在 25 DAP 下调。与 Mo17 相比。通过对小 RNA 和降解组序列的综合分析，鉴定出 22 个差异表达的 miRNA，包括 14 个已知和 8 个以前未知的 miRNA，它们可以靶向 35 个基因。此外，构建了一个复杂的共表达调控网络，其中 19 个 miRNA 可以通过调节 19 个靶基因的表达来调节胚乳中的淀粉生物合成。此外，通过表达模式分析、瞬时转化测定和反式激活测定，验证了涉及转录因子 miR169a-NF-YA1-GBSSI/SSIIIa 和 miR169o-GATA9-SSIIIa/SBEIIb 的四条 miRNA 介导途径的潜在操作。
我们的研究结果表明，miRNA 在胚乳淀粉生物合成中发挥着重要作用，miRNA 介导的网络可以调节该组织中的淀粉生物合成。这些结果为研究玉米胚乳淀粉生物合成的分子机制提供了重要线索。
