Inhibition of lateral shoot formation by RNA interference and chemically induced mutations to genes expressed in the axillary meristem of Nicotiana tabacum L.

backgroundLateral branches vigorously proliferate in tobacco after the topping of the inflorescence portions of stems for the maturation of the leaves to be harvested. Therefore, tobacco varieties with inhibited lateral shoot formation are highly desired by tobacco farmers.

resultsGenetic inhibition of lateral shoot formation was attempted in tobacco. Two groups of genes were examined by RNA interference. The first group comprised homologs of the genes mediating lateral shoot formation in other plants, whereas the second group included genes highly expressed in axillary bud primordial stages. Although "primary" lateral shoots that grew after the plants were topped off when flower buds emerged were unaffected, the growth of "secondary" lateral shoots, which were detected on the abaxial side of the primary lateral shoot base, was significantly suppressed in the knock-down lines of NtLs, NtBl1, NtREV, VE7, and VE12. Chemically induced mutations to NtLs, NtBl1, and NtREV similarly inhibited the development of secondary and "tertiary" lateral shoots, but not primary lateral shoots. The mutations to NtLs and NtBl1 were incorporated into an elite variety by backcrossing. The agronomic characteristics of the backcross lines were examined in field trials conducted in commercial tobacco production regions. The lines were generally suitable for tobacco leaf production and may be useful as new tobacco varieties.

conclusionThe suppressed expression of NtLs, NtBl1, NtREV, VE7, or VE12 inhibited the development of only the secondary and tertiary lateral shoots in tobacco. The mutant lines may benefit tobacco farmers by minimizing the work required to remove secondary and tertiary lateral shoots that emerge when farmers are harvesting leaves, which is a labor-intensive process.