National Institute of Plant Genome Research, Aruna Asaf Ali Marg, PO Box No. 10531, New Delhi, 110 067, India.
Planta. 2020 Jan 24;251(2):55. doi: 10.1007/s00425-020-03346-w.
Expansion of MIR169 members by duplication and new mature forms, acquisition of new promoters, differential precursor-miRNA processivity and engaging novel targets increase the functional diversification of MIR169 in tomato. MIR169 family is an evolutionarily conserved miRNA family in plants. A systematic in-depth analysis of MIR169 family in tomato is lacking. We report 18 miR169 precursors, annotating new loci for MIR169a, b and d, as well as 3 novel mature isoforms (MIR169f/g/h). The family has expanded by both tandem- and segmental-duplication events during evolution. A tandem-pair MIR169b/b-1 and MIR169b-2/h is polycistronic in nature coding for three MIR169b isoforms and a new variant miR169h, that is evidently absent in the wild relatives S. pennellii and S. pimpinellifolium. Seven novel miR169 targets including RNA-binding protein, protein-phosphatase, aminotransferase, chaperone, tetratricopeptide-repeat-protein, and transcription factors ARF-9B and SEPELLATA-3 were established by efficient target cleavage in the presence of specific precursors as well as increased target abundance upon miR169 chelation by short-tandem-target-mimic construct in transient assays. Comparative antagonistic expression profiles of MIR169:target pairs suggest MIR169 family as ubiquitous regulator of various abiotic stresses (heat, cold, dehydration and salt) and developmental pathways. This regulation is partly brought about by acquisition of new promoters as demonstrated by promoter MIR169:GUS reporter assays as well as differential processivity of different precursors and miRNA cleavage efficiencies. Thus, the current study augments the functional horizon of MIR169 family with applications for stress tolerance in crops.
MIR169 成员通过复制和新的成熟形式的扩张，获得新的启动子，差异前体-miRNA 连续性和参与新的靶标，增加了番茄中 MIR169 的功能多样化。MIR169 家族是植物中进化上保守的 miRNA 家族。番茄中 MIR169 家族的系统深入分析还缺乏。我们报告了 18 个 miR169 前体，为 MIR169a、b 和 d 注释了新的基因座，以及 3 个新的成熟同工型（MIR169f/g/h）。该家族在进化过程中通过串联和片段复制事件而扩张。MIR169b/b-1 和 MIR169b-2/h 的串联对本质上是多顺反子，编码三个 MIR169b 同工型和一个新的变体 miR169h，这在野生亲缘种 S. pennellii 和 S. pimpinellifolium 中显然不存在。通过在存在特定前体的情况下有效靶标切割以及在瞬时测定中通过短串联靶标模拟构建物螯合 miR169 后靶标丰度增加，建立了 7 个新的 miR169 靶标，包括 RNA 结合蛋白、蛋白磷酸酶、氨基转移酶、伴侣蛋白、四肽重复蛋白和转录因子 ARF-9B 和 SEPELLATA-3。在瞬时测定中，通过特异性前体切割和 miR169 螯合后靶标丰度的增加，建立了 7 个新的 miR169 靶标，包括 RNA 结合蛋白、蛋白磷酸酶、氨基转移酶、伴侣蛋白、四肽重复蛋白和转录因子 ARF-9B 和 SEPELLATA-3。在瞬时测定中，通过特异性前体切割和 miR169 螯合后靶标丰度的增加，建立了 7 个新的 miR169 靶标，包括 RNA 结合蛋白、蛋白磷酸酶、氨基转移酶、伴侣蛋白、四肽重复蛋白和转录因子 ARF-9B 和 SEPELLATA-3。通过特异性前体切割和 miR169 螯合后靶标丰度的增加，建立了 7 个新的 miR169 靶标，包括 RNA 结合蛋白、蛋白磷酸酶、氨基转移酶、伴侣蛋白、四肽重复蛋白和转录因子 ARF-9B 和 SEPELLATA-3。
比较拮抗表达谱表明，MIR169 家族是各种非生物胁迫（热、冷、脱水和盐）和发育途径的普遍调节因子。这种调控部分是通过获得新的启动子来实现的，这可以通过启动子 MIR169:GUS 报告基因检测以及不同前体的差异连续性和 miRNA 切割效率来证明。因此，本研究通过在作物中应用耐胁迫来扩展 MIR169 家族的功能范围。
