Transcriptional control of cellular reprogramming during the symbiotic interaction of Medicago truncatula with arbuscular mycorrhizal fungi

丛枝菌根(AM)是地球上最广泛的有益植物-微生物相互作用。由于模式豆科植物紫花苜蓿和模式AM真菌Glomus inaradices的全面序列信息的可用性，全基因组表达谱实验是可能的。为了了解AM相关的转录重编程，我们研究了三个水平的信号：感受可扩散的Myc因子的根真皮细胞，被菌根真菌感染的根细胞，以及建立功能丛枝的皮质细胞。由于Myc因子与根瘤菌结瘤因子类似，是以脂壳低聚糖的形式出现的，因此我们将利用共生突变体来区分Nod因子和Myc因子信号，以阐明Myc因子的特异性反应。通过激光显微切割，研究AM早期和晚期细胞特异性基因的表达。在这些实验的基础上，可以开发Myc因子活性的原位标记，并进一步研究与调控含丛生植物细胞基因表达相关的启动子基序。通过转录组分析选择的候选基因继续进行反向遗传学，以研究它们在早期和晚期细胞重新编程中的作用。到目前为止，已发现的候选基因与钙/钙调蛋白依赖的蛋白激酶DMI3的上游和下游的AM早期信号有关，或者在含丛生植物的细胞中表达。总共有12个Tnt1插入突变系可用，除了RNAi方法外，现在还可以用于详细的功能研究。

Arbuscular mycorrhizae (AM) are the most widespread beneficial plant-microbe interactions on Earth. Due to the availability of comprehensive sequence information for the model legume Medicago truncatula and the model AM fungus Glomus intraradices, genome-wide expression profiling experiments are possible. To understand AM-related transcriptional reprogramming, we investigate three levels of signaling: rhizodermal cells perceiving diffusible Myc-factors, root cells infected by mycorrhizal fungi, and cortical cells establishing functional arbuscules. Since Myc-factors emerged as lipochitooligosaccharides similar to rhizobial Nod-factors, we will use symbiotic mutants to discriminate Nod- and Myc-factor signaling, in order to elucidate Myc-factor specific responses. Via laser microdissection, cell-specific gene expression during early and late AM stages is investigated. Based on these experiments, in situ markers for Myc-factor activity can be developed, and promoter motifs related to the control of gene expression in arbuscule-containing cells will be studied further. Reverse genetics continues to be performed for candidate genes selected by transcriptome profiling to investigate their role during early and late cellular reprogramming. Candidate genes identified so far are related to early AM signaling upstream and downstream of the calcium/calmodulin-dependent protein kinase DMI3, or are expressed in arbuscule-containing cells. In total, 12 Tnt1 insertion mutant lines are available that in addition to RNAi approaches can now be used for detailed functional studies.