Cytokinin-Dependent Control of <i>GH3</i> Group II Family Genes in the <i>Arabidopsis</i> Root
Emanuela Pierdonati,
Simon Josef Unterholzner,
Elena Salvi,
Noemi Svolacchia,
Gaia Bertolotti,
Raffaele Dello Ioio,
Sabrina Sabatini,
Riccardo Di Mambro
Affiliations
Emanuela Pierdonati
Dipartimento di Biologia e Biotecnologie, Laboratory of Functional Genomics and Proteomics of Model Systems, Università di Roma, Sapienza-via dei Sardi, 70–00185 Rome, Italy
Simon Josef Unterholzner
Dipartimento di Biologia e Biotecnologie, Laboratory of Functional Genomics and Proteomics of Model Systems, Università di Roma, Sapienza-via dei Sardi, 70–00185 Rome, Italy
Elena Salvi
Dipartimento di Biologia e Biotecnologie, Laboratory of Functional Genomics and Proteomics of Model Systems, Università di Roma, Sapienza-via dei Sardi, 70–00185 Rome, Italy
Noemi Svolacchia
Dipartimento di Biologia e Biotecnologie, Laboratory of Functional Genomics and Proteomics of Model Systems, Università di Roma, Sapienza-via dei Sardi, 70–00185 Rome, Italy
Gaia Bertolotti
Dipartimento di Biologia e Biotecnologie, Laboratory of Functional Genomics and Proteomics of Model Systems, Università di Roma, Sapienza-via dei Sardi, 70–00185 Rome, Italy
Raffaele Dello Ioio
Dipartimento di Biologia e Biotecnologie, Laboratory of Functional Genomics and Proteomics of Model Systems, Università di Roma, Sapienza-via dei Sardi, 70–00185 Rome, Italy
Sabrina Sabatini
Dipartimento di Biologia e Biotecnologie, Laboratory of Functional Genomics and Proteomics of Model Systems, Università di Roma, Sapienza-via dei Sardi, 70–00185 Rome, Italy
Riccardo Di Mambro
Department of Biology, University of Pisa-via L. Ghini, 13–56126 Pisa, Italy
The Arabidopsis root is a dynamic system where the interaction between different plant hormones controls root meristem activity and, thus, organ growth. In the root, a characteristic graded distribution of the hormone auxin provides positional information, coordinating the proliferating and differentiating cell status. The hormone cytokinin shapes this gradient by positioning an auxin minimum in the last meristematic cells. This auxin minimum triggers a cell developmental switch necessary to start the differentiation program, thus, regulating the root meristem size. To position the auxin minimum, cytokinin promotes the expression of the IAA-amido synthase group II gene GH3.17, which conjugates auxin with amino acids, in the most external layer of the root, the lateral root cap tissue. Since additional GH3 genes are expressed in the root, we questioned whether cytokinin to position the auxin minimum also operates via different GH3 genes. Here, we show that cytokinin regulates meristem size by activating the expression of GH3.5 and GH3.6 genes, in addition to GH3.17. Thus, cytokinin activity provides a robust control of auxin activity in the entire organ necessary to regulate root growth.
