RLT-mediated Study Of Callus Pluripotency

Regeneration is a process of renewal,restoration,and growth of life.It enables organisms to better adapt to fluctuations in the natural environment or to survive after damage.Plants have long been observed to have a strong ability to regenerate.It has been observed 60 years that explant,under the stimulation of auxin and cytokinin,can grow callus and secondary organs,like adventitious root or adventitious shoot.For a long time,we have agreed that the process of callus proliferation is a process of dedifferentiation,that is,the process of dedifferentiation by terminally differentiated cells to form undifferentiated disordered cell masses and to differentiate into roots or shoots.However,Sugimoto et al.noticed that the process of callus proliferation was not dedifferentiation but a process resembles the initiation of lateral roots.And callus is a cluster of pluripotent cell mass that resembles root tip.Reasearch in this field has made it clear that the essence of regeneration is cell fate transformation under wound or stress signals.Based on this,our laboratory established a classical pathway for the initiation of adventitious roots,namely the transformation from the competent cells in the leaf vascular tissue to the WOX11 labeled adventitious root founder cells and then to the root primordial cells labeled by WOX5 and LBD16.Epigenetics refers to DNA-independent nuclear inheritance.ISWI is a type of chromatin remodeling factor with two members in Arabidopsis: CHR11,CHR17.ISWI is a highly conserved protein in eukaryotes.It was first discovered in Drosophila and its biochemical function mainly is sliding nucleosomes.But its function in de novo organogenesis is not clear.We previously identified that the leaf explants undergo a process of downregulation of leaf trait genes and upregulation of root trait genes orderly in the process of callus induction.However,through microarray,we found that in chr11-1chr17-1 background,leaf genes can normally be downregulated,but the root attribute genes cannot properly be upregulated.We speculate that ISWI is the key regulator of root genes in callus development.However,the specific mechanism is not clear,and my work focuses on RLT that interacts with ISWI and has similar developmental and regeneration defects.ISWI itself may not have a known domain that recognizes DNA sequences,nor does it have a domain that recognizes histone modifications.How does its specificity manifest? We believe that its specificity is determined by the companion protein RLT which has DNA binding domain.At the initial stage of callus formation,my data shows that it resemble the wild type.However,I noticed that the callus pluripotency marker gene LBD16 was abnormally regulated in the context of rlt1-1rlt2-1.And this also supports the previous hypothesis: ISWI-RLT complex controls the callus root genes.In addition,WUS is not normally expressed under rlt1-1rlt2-1 background in SIM medium.Considering the importance of WUS in shoot apical meristem reconstruction,I think that the ISWI-RLT complex may partially control the root properties of callus at least through LBD16 and result in WUS abnormally expression.My work revealed an important mechanism for the acquisition of callus pluripotency from callus to shoot.This study can theoretically enrich the understanding of the mechanism of callus pluripotency acquisition and regeneration.On the other hand,it also has important practical value in guiding the application of agriculture and horticulture.