Functional genomics of the periderm: the biosynthetic gene FHT, the transcriptional regulator StRiK and the transcriptome deciphering

We have developed new molecular tools to characterize the FHT and StRIK genes in the tuber periderm. Regarding FHT gene, our results demonstrated that is induced very specifically in suberizing tissues what makes FHT a good marker of the suberization process. Regarding StRIK gene, it has been shown to be a good candidate for the periderm regulation since its silencing causes changes in genes expression related to the transposition of DNA, RNA processing and stress. Finally, by RNA-seq we have identified a wide range of new candidate genes for the formation of the cork oak periderm. Among these genes several are related to the formation of the cell wall, cell primary metabolism and suberin accumulation. Other relevant genes are those involved in the regulation of meristem such as auxin transporters and the ethylene metabolism and signaling. The expression patterns of some genes have been studied during the cork growing season.Hem desenvolupat noves eines moleculars per a la caracterització dels gens FHT i StRIK en el peridermis del tubercle. Els nostres resultats mostren que FHT s’indueix de forma molt específica en teixits suberificats el que el fa un bon marcador del procés de suberificació. En relació al gen StRIK, hem vist que es un bon candidat a la regulació de la peridermis ja que el seu silenciament provoca canvis d’expressió en gens relacionats amb la transposició de l’ADN, el processament de l’RNA i l’estrès. Mitjançant RNA-seq hem identificat nous gens candidats per la formació de la peridermis en l’alzina surera, entre ells destaquen gens relacionats amb la formació de la paret cel·lular, el metabolisme primari i l’acumulació de suberina. També destaquen gens relacionats amb la regulació del meristema com ara els transportadors d’auxines i el metabolisme i senyalització per etilè. L’expressió d’alguns gens s’ha analitzat durant la formació del suro

The potato suberin feruloyl transferase FHT which accumulates in the phellogen is induced by wounding and regulated by abscisic and salicylic acids

The present study provides new insights on the role of the potato (Solanum tuberosum) suberin feruloyl transferase FHT in native and wound tissues, leading to conclusions about hitherto unknown properties of the phellogen. In agreement with the enzymatic role of FHT, it is shown that its transcriptional activation and protein accumulation are specific to tissues that undergo suberization such as the root boundary layers of the exodermis and the endodermis, along with the tuber periderm. Remarkably, FHT expression and protein accumulation within the periderm is restricted to the phellogen derivative cells with phellem identity. FHT levels in the periderm are at their peak near harvest during periderm maturation, with the phellogen becoming meristematically inactive and declining thereafter. However, periderm FHT levels remain high for several months after harvest, suggesting that the inactive phellogen retains the capacity to synthesize ferulate esters. Tissue wounding induces FHT expression and the protein accumulates from the first stages of the healing process onwards. FHT is up-regulated by abscisic acid and down-regulated by salicylic acid, emphasizing the complex regulation of suberin synthesis and wound healing. These findings open up new prospects important for the clarification of the suberization process and yield important information with regard to the skin quality of potatoesThe authors thank Professor S. Prat (Centro Nacional de Biotecnologia, Madrid) and Dr E. Dominguez (Centre de Recerca en Agrigenomica CRAG, Barcelona) for providing potato ssp. andigena, for support, and for helpful experimental advice; Dr P. Suarez (CRAG) for kindly lending us the ultracentrifuge; Professor D. Ludevid, Dr S. Irar, and Dr M. P. Gonzalez (CRAG), and Dr T. Roscoe (Institut de Recherche pour le Development, Montpellier) for fruitful suggestions regarding protein and antibody production, immunolocalization, and GUS staining; and Dr J. Castro (Biology Department, University of Girona, UdG) for helpful advice on setting up the western blot conditions. We also thank Mr J. Blavia and D. Reyes (Serveis Tecnics de Recerca, UdG) and S. Gomez (Departament de Biologia, UdG) for their valuable assistance in carrying out the laboratory work. This work was supported by the Ministerio de Innovacion y Ciencia [AGL2009-13745], the Ministerio de Educacion y Ciencia [FPI grant to PB], and the Ministerio de Economia y Competitividad [AGL2012-36725