Abstract
De novo organ regeneration is an excellent biological system for the study of fundamental questions regarding stem cell initiation, cell fate determination, and hormone signaling. Despite the general belief that auxin and cytokinin responses interact to regulate de novo organ regeneration, the molecular mechanisms underlying such a cross talk are little understood. Here, we show that spatiotemporal biosynthesis and polar transport resulted in local auxin distribution in Arabidopsis (Arabidopsis thaliana), which in turn determined the cytokinin response during de novo shoot regeneration. Genetic and pharmacological interference of auxin distribution disrupted the cytokinin response and ATP/ADP ISOPENTENYLTRANSFERASE5 (AtIPT5) expression, affecting stem cell initiation and meristem formation. Transcriptomic data suggested that AUXIN RESPONSE FACTOR3 (ARF3) mediated the auxin response during de novo organ regeneration. Indeed, mutations in ARF3 caused ectopic cytokinin biosynthesis via the misexpression of AtIPT5, and this disrupted organ regeneration. We further showed that ARF3 directly bound to the promoter of AtIPT5 and negatively regulated AtIPT5 expression. The results from this study thus revealed an auxin-cytokinin cross talk mechanism involving distinct intermediate signaling components required for de novo stem cell initiation and shed new light on the mechanisms of organogenesis in planta.
Highlights
Plant cells have an amazing capacity to regenerate organs from differentiated somatic tissues under appropriate culture conditions, a process designated de novo organogenesis
We induced callus formation from plant pistils in an auxin-rich callus induction medium (CIM), and transferred the calli onto a cytokinin-rich shoot induction medium (SIM) for shoot induction (Cheng et al, 2010), and we suggested that the expression of WUS/CLAVATA (CLV3) marked stem cell initiation and shoot meristem formation is developmentally regulated during these processes (Su et al, 2010)
These results show that the distribution pattern of the auxin response is mutually exclusive of WUS expression during stem cell induction and shoot meristem formation
Summary
Plant cells have an amazing capacity to regenerate organs from differentiated somatic tissues under appropriate culture conditions, a process designated de novo organogenesis. The first step involves the formation of the callus, a mass of undifferentiated pluripotent cells derived from various explant tissues grown on callus induction medium (CIM) that has a high auxin/cytokinin ratio. Depending on the auxin/cytokinin ratios of the induction medium, either shoots or roots can be regenerated (Skoog and Miller, 1957; Bhojwani and Razdan, 1996; Che et al, 2002). De novo shoot formation is highly controlled, and can serve as an excellent experimental system to study fundamental biological processes such as stem cell initiation, cell fate determination, cell differentiation, and hormonal crosstalk (Che et al, 2006; Birnbaum and Sánchez, 2008)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.