Transcriptome Analysis of Shade-Induced Inhibition on Leaf Size in Relay Intercropped Soybean

Multi-species intercropping is a sustainable agricultural practice worldwide used to utilize resources more efficiently. In intercropping systems, short crops often grow under vegetative shade of tall crops. Soybean, one important legume, is often planted in intercropping. However, little is known about the mechanisms of shade inhibition effect on leaf size in soybean leaves at the transcriptome level. We analyzed the transcriptome of shaded soybean leaves via RNA-Seq technology. We found that transcription 1085 genes in mature leaves and 1847 genes in young leaves were significantly affected by shade. Gene ontology analyses showed that expression of genes enriched in polysaccharide metabolism was down-regulated, but genes enriched in auxin stimulus were up-regulated in mature leaves; and genes enriched in cell cycling, DNA-replication were down-regulated in young leaves. These results suggest that the inhibition of higher auxin content and shortage of sugar supply on cell division and cell expansion contribute to smaller and thinner leaf morphology, which highlights potential research targets such as auxin and sugar regulation on leaves for crop adaptation to shade in intercropping.多物种间作是全球范围内广泛应用的可持续农业种植模式，可更高效地利用自然资源。在间作系统中，矮秆作物通常生长在高秆作物的营养生长遮荫环境下。大豆作为重要的豆科作物，常被应用于间作种植体系中。然而，目前学界对遮荫抑制大豆叶片叶形大小的分子机制，在转录组层面的研究仍较为匮乏。本研究通过RNA测序（RNA-Seq）技术对遮荫处理后的大豆叶片转录组进行了分析。研究发现，遮荫处理显著影响了成熟叶片中1085个基因、幼嫩叶片中1847个基因的转录水平。基因本体（Gene Ontology, GO）富集分析结果显示，成熟叶片中富集于多糖代谢通路的基因表达量显著下调，而富集于生长素刺激响应通路的基因表达量显著上调；幼嫩叶片中富集于细胞周期、DNA复制通路的基因表达量则显著下调。上述研究结果表明，高生长素含量与糖供给不足对细胞分裂与细胞扩张的抑制作用，共同导致了大豆叶片形态变小、变薄的表型；该发现为间作体系中作物适应遮荫环境的调控靶点（如叶片生长素与糖分调控）提供了潜在的研究方向。