Male sterile lines play important roles in plant breeding to obtain hybrid vigour. The male sterility Lembke (MSL) system is a thermosensitive genic male sterility system of Brassica napus and is one of the main systems used in European rapeseed breeding. Interestingly the MSL system shows high similarity to the 9012AB breeding system from China including the ability to revert to fertile in high temperature conditions. Here we demonstrate that the MSL system is regulated by the same restorer of fertility gene BnaC9-Tic40 as the 9012AB system, which is related to the translocon at the inner envelope membrane of chloroplasts 40 (TIC40) from Arabidopsis. The male sterility gene of the MSL system was also identified to be a chloroplast localised protein which we call BnChimera, this gene shows high sequence similarity to the sterility gene previously described for the 9012AB system. For the first time a direct protein interaction between the BnaC9-Tic40 and the BnChimera could be demonstrated. In addition, the corresponding amino acids that mediate this interaction were identified and possibly determine how BnaC9-Tic40 acts as the restorer of fertility. Using an RNA-seq approach, the effects of heat treatment on the male fertility restoration of an MSL system line C545 were investigated. This data demonstrated that many pollen developmental pathways were affected by the higher temperatures. It is hypothesised that heat stress reverses the male sterility via a combination of slower production of cell wall precursors in plastids and a slower flower development, which ultimately results in fertile pollen. The potential breeding applications of these results are discussed regarding the capacity of using the MSL system in producing thermotolerant fertile plants.
FörderungenHelmholtz Association Center for Integrated Protein Science Munich (CIPSM) European Commission Technical University of Munich, Institute for Advanced Study - German Excellence Initiative