A putative bHLH transcription factor is a candidate gene for male sterile 32, a locus affecting pollen and tapetum development in tomato

Abstract

The tomato (Solanum lycopersicum) male sterile 32 (ms32) mutant has been used in hybrid seed breeding programs largely because it produces no pollen and has exserted stigmas. In this study, histological examination of anthers revealed dysfunctional pollen and tapetum development in the ms32 mutant. The ms32 locus was fine mapped to a 28.5 kb interval that encoded four putative genes. Solyc01g081100, a homolog of Arabidopsis bHLH10/89/90 and rice EAT1, was proposed to be the candidate gene of MS32 because it contained a single nucleotide polymorphism (SNP) that led to the formation of a premature stop codon. A codominant derived cleaved amplified polymorphic sequence (dCAPS) marker, MS32D, was developed based on the SNP. Real-time quantitative reverse-transcription PCR showed that most of the genes, which were proposed to be involved in pollen and tapetum development in tomato, were downregulated in the ms32 mutant. These findings may aid in marker-assisted selection of ms32 in hybrid breeding programs and facilitate studies on the regulatory mechanisms of pollen and tapetum development in tomato.

Knockout of SlMS10 Gene (Solyc02g079810) Encoding bHLH Transcription Factor Using CRISPR/Cas9 System Confers Male Sterility Phenotype in Tomato

“…In addition, the application of male sterility is a very efficient approach to reducing hybrid seed costs and ensuring high varietal purity [ 2 ]. Since the first description by Crane [ 4 ], tomato male sterility has been an interest for many researchers, and so far about 50 male sterility mutants have been reported [ 5 , 15 , 16 , 17 , 18 , 19 , 24 , 41 , 42 , 43 , 44 ]. These spontaneous male-sterile mutants are an excellent system for integrating male sterility for hybrid seed production.…”

“…Among transcription factors, the basic helix-loop-helix (bHLH) proteins play an important role in plant growth and development. A total of 152 bHLH transcription factors have been reported in the tomato genome [ 15 , 16 , 17 , 18 , 19 , 20 ]. The bHLH motif consists of two functionally distinct regions: the basic region for DNA binding and the HLH region for protein dimerization [ 21 ].…”

“…It has been reported that the SlMS10 gene encoding a basic helix-loop-helix transcription factor (bHLH), which carries both programmed cell death and meiosis in the tapetum during microsporogenesis [ 24 ]. Molecular marker development and gene targeting have been reported for other genes controlling male sterility such as ms10 , ms15 , ms32 , ps2 (positional sterile 2), ex (exserted stigma) and 7B−1 for tomato breeding [ 18 , 19 , 24 , 25 , 26 , 27 ]. In that work, male-sterile tomato lines were generated by CRSIPR-CAS9 induced knockout of a stamen-specific gene SlSTR1 [ 28 ].…”

A biotechnology‐based male‐sterility system for hybrid seed production in tomato

“…Male sterility of tomato has been paid great attention by plant breeders since the first mutant was described in 1915, and the use of male sterility for producing tomato hybrid seeds has been widely discussed (Crane, ; Gorman and McCormick, ; Sawhney, ). To this purpose, different genes controlling male sterility including male‐sterile‐10 ( ms‐10 ), ms‐15 , ms‐32 , positional sterile‐2 ( ps‐2 ), exserted stigma ( ex ) and 7B‐1 have been studied, and several ideas and systems for their efficacious application have been developed and tested (Crane, ; Gorman and McCormick, ; Atanassova and Georgiev, ; Sawhney, ; Cheema and Dhaliwal, ; Gorguet et al , ; Jeong et al , ; Quinet et al , ; Zhang et al , ; Pucci et al , ; Cao et al , ; Liu et al , ). However, until present, male‐sterile lines have not been used on a large scale in tomato hybrid seed production.…”

“…Although many recessive genic male‐sterile tomato mutations are useful for producing hybrid seeds (Atanassova and Georgiev, ; Gorguet et al , ; Jeong et al , ; Quinet et al , ; Zhang et al , ; Pucci et al , ; Cao et al , ; Liu et al , ), two major factors have limited their commercial application: the difficulty of propagating large quantities of pure male‐sterile seeds (Perez‐Prat and van Lookeren Campagne, ; Chang et al , ; Wu et al , ); and the fact that traditional backcrossing requires a long time and many generations to transfer recessive male sterility into other genetic backgrounds. The classic approach to obtain seeds of homozygous male‐sterile plants is to cross‐pollinate homozygous male‐sterile plants (ms/ms) with heterozygote male‐fertile (Ms/ms) plants.…”