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

Kaori Hamano,Seiki Sato,Yuta Negishi,Tomoyuki Komatsu,Tsuyoshi Naragino,Shoichi Suzuki,Masao Arai,Takashi Nakamura

doi:10.1186/s12870-021-03008-3

Abstract

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.

Highlights

Lateral branches vigorously proliferate in tobacco after the topping of the inflorescence portions of stems for the maturation of the leaves to be harvested
Basic local alignment search tool (BLAST) search Two groups of tobacco genes were examined to assess the effects of RNA interference (RNAi) knock-down on lateral shoot formation
Because tobacco is an amphidiploid species that inherited its genome from Nicotiana sylvestris (S-genome) and Nicotiana tomentosiformis (T-genome) [22,23,24], both S-genes and T-genes were identified for each homolog

Summary

Introduction

Lateral branches vigorously proliferate in tobacco after the topping of the inflorescence portions of stems for the maturation of the leaves to be harvested. Lateral shoot development, which is a fundamental process in plants, is uniquely regulated in all species. Three Regulator of Axillary Meristems (RAX) genes, RAX1, RAX2, and RAX3, were identified in Arabidopsis as homologs of Blind. Blind and RAX genes encode R2R3 MYB transcription factors, which are critical for initiating axillary meristem development during the vegetative phase. The LAX1 gene in rice and the BA1 gene in maize encode bHLH domains and are involved in the branching of inflorescence and vegetative shoots [8, 9]. The ROX gene in Arabidopsis is an ortholog of LAX1 and BA1. It is reportedly involved in lateral shoot formation in the early vegetative stage [10]

Results

Discussion

Conclusion