BLADE-ON-PETIOLE genes are not involved in the transition from protonema to gametophore in the moss Physcomitrella patens
The timing of the transition between developmental phases is a critical determinant of plant form. In the moss Physcomitrella patens, the transition from protonema to gametophore is a particularly important step as it results in a change from two-dimensional to three-dimensional growth of the plant body. It is well known that this transition is promoted by cytokinin (CK), however, the underlying mechanisms are poorly understood. Previously, it was reported that P. patens orthologs of BLADE-ON-PETIOLE (BOP) genes (PpBOPs) work downstream of CK to promote the transition to gametophore. To further understand the role of PpBOPs in the control of this transition, we performed functional analyses of PpBOP genes. We simultaneously disrupted the function of all three PpBOP genes in P. patens using CRISPR technology, however, no abnormal phenotypes were observed in the triple mutant during either the gametophytic or the sporophytic growth stages. CK treatment did not alter the phase change in the triple mutant. We conclude that PpBOP genes are unnecessary in the control of P. patens development under normal conditions. We propose that BOP genes are not involved in the control of developmental processes in bryophytes and other basal land plants, but may function in physiological processes such as in the defense response.
KeywordsBLADE-ON-PETIOLE (BOP) Bryophyte Cytokinin Physcomitrella patens Triple loss-of-function mutant
We thank Dr. Yuji Hiwatashi (Miyagi University) for providing the P. patens Gransden strain and for teaching us how to culture and transform P. patens. We thank Dr. Emiko Yoro (Rikkyo University) for teaching us sporophyte induction. We also thank Dr. Fabien Nogue (INRA Centre de Versailles-Grignon) for providing the pBNRF, pAct-Cas9 and sgRNA plasmids. This work was supported by JSPS/MEXT Kakenhi grants to JK (22119008, 22247004, 16K14748, 17H06475, 18K19198) and SN (17K17595).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.