Synchronization of Developmental Processes and Defense Signaling by Growth Regulating Transcription Factors

Growth regulating factors (GRFs) are a conserved class of transcription factor in seed plants. GRFs are involved in various aspects of tissue differentiation and organ development. The implication of GRFs in biotic stress response has also been recently reported, suggesting a role of these transcription factors in coordinating the interaction between developmental processes and defense dynamics. However, the molecular mechanisms by which GRFs mediate the overlaps between defense signaling and developmental pathways are elusive. Here, we report large scale identification of putative target candidates of Arabidopsis GRF1 and GRF3 by comparing mRNA profiles of the grf1/grf2/grf3 triple mutant and those of the transgenic plants overexpressing miR396-resistant version of GRF1 or GRF3. We identified 1,098 and 600 genes as putative targets of GRF1 and GRF3, respectively. Functional classification of the potential target candidates revealed that GRF1 and GRF3 contribute to the regulation of various biological processes associated with defense response and disease resistance. GRF1 and GRF3 participate specifically in the regulation of defense-related transcription factors, cell-wall modifications, cytokinin biosynthesis and signaling, and secondary metabolites accumulation. GRF1 and GRF3 seem to fine-tune the crosstalk between miRNA signaling networks by regulating the expression of several miRNA target genes. In addition, our data suggest that GRF1 and GRF3 may function as negative regulators of gene expression through their association with other transcription factors. Collectively, our data provide new insights into how GRF1 and GRF3 might coordinate the interactions between defense signaling and plant growth and developmental pathways.生长调节因子（growth regulating factors，GRFs）是种子植物中一类保守的转录因子。GRFs广泛参与植物组织分化与器官发育的诸多过程。近期研究还报道了GRFs在生物胁迫响应中的调控作用，表明这类转录因子可协调植物发育进程与防御动态之间的相互作用。然而，GRFs介导防御信号通路与发育通路之间交叉互作的分子机制仍未阐明。本研究通过对比grf1/grf2/grf3三突变体与过表达抗miR396的GRF1或GRF3变体的转基因植株的mRNA表达谱，大规模鉴定了拟南芥（Arabidopsis）GRF1与GRF3的潜在靶标候选基因。本研究分别鉴定得到1098个和600个GRF1、GRF3的潜在靶标基因。对潜在靶标候选基因的功能分类分析显示，GRF1与GRF3参与调控与防御响应及抗病性相关的多种生物学过程。GRF1与GRF3还特异性参与防御相关转录因子、细胞壁修饰、细胞分裂素生物合成与信号通路以及次生代谢产物积累的调控。GRF1与GRF3可通过调控多个miRNA靶基因的表达，精细调控miRNA信号网络之间的交叉互作。此外，本研究数据显示GRF1与GRF3可通过与其他转录因子结合，作为基因表达的负调控因子发挥功能。综上，本研究数据为解析GRF1与GRF3如何协调防御信号通路与植物生长发育通路之间的相互作用提供了新的视角。