Snap bean (Phaseolus vulgaris L.) is an important vegetable crop worldwide. Generally, the fresh pod is the main edible part for human consumption.

To date, functional studies on male sterility in common bean have rarely been reported. Aiming to create rich genetic variations for studying gene function, a mutant library of the common bean cultivar ‘Dalong1’ of the golden hook ecotype was developed by professor Xia’s research group from Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences.

Recently, the researchers characterized a mutant carrying the genic male sterility (ms-2) mutation and unveiled that the Phvul.003G031200 (PvTKPR2) gene is the causal gene for the MS-2 gene by fine mapping. Based on the re-sequencing data for ‘Dalong1’ and the ms-2 mutant, this study revealed that a novel 7-bp (+ 6028 bp to + 6034 bp) deletion spanning the splice site between the fourth intron and fifth exon, leading to a 9-bp deletion at transcribed mRNA level and a 3-amino acid (G210M211V212) deletion at AA level of the PvTKPR2^ms-2 gene. The 3-D structural changes in the protein due to the mutation may impair the activities of NAD-dependent epimerase/dehydratase and the NAD(P)-binding domains of PvTKPR2^ms-2 protein.

This work was published in the journal Theoretical and Applied Genetics on March 13.

The researchers compared microspore development in the anther lobes at four developmental stages in the WT and the ms-2 mutant and found that premature degradation of the tapetum might be the key mechanism regulating male sterility in the MS-2 mutant.

Since ms-2 mutant plants can produce a large number of seedless pods, the researchers tested the potential of the parthenocarpic pods of ms-2 as a vegetable for human consumption. According to the previous report, auxin can promote ovary growth and parthenocarpic fruit setting. After external application of 2 mM IAA to the ms-2 mutant, the pod was doubled in size in terms of its length, width, and thickness, and its fresh weight was proportionally increased.

This study demonstrates that a splicing mutation in the MS-2 gene causes pollen-less anthers and triggers parthenocarpic fruit development in snap bean. Exogenous treatment with auxin leads to enlargement of the parthenocarpic pods in ms-2 mutant plants.

The full information of the article:

Kun Xu, Jinlong Zhu, Ning Guo, Jinyu Liu, Hong Zhai, Xiaobin Zhu, Yi Gao, Hongyan Wu, Zhengjun Xia. A novel 7-base pair deletion at a splice site in MS-2 impairs male fertility via premature tapetum degradation in common bean (Phaseolis vulgaris L.). Theor Appl Genet 2023, 136, 56.

https://doi.org/10.1007/s00122-023-04255-8

Contact

Zhengjun Xia

Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences

E-mail: xiazhj@neigaehrb.ac.cn