Miki Ogasawara, Naoya Miyazaki, Gotaro Monden, Kenta Taniko, Sathya Lim, Masahide Iwata, Takashige Ishii, Jian Feng Ma & Ryo Ishikawa

Theoretical and Applied Genetics September 2021, vol. 134: 3013–3022 

Key message

A candidate gene responsible for higher grain zinc accumulation in rice was identified, which was probably associated with a partial defect in anther dehiscence.

Abstract

Zinc (Zn) is an essential mineral element in many organisms. Zn deficiency in humans causes various health problems; therefore, an adequate dietary Zn intake is required daily. Rice, Oryza sativa, is one of the main crops cultivated in Asian countries, and one of the breeding scopes of rice is to increase the grain Zn levels. Previously, we found that an Australian wild rice strain, O. meridionalis W1627, exhibits higher grain Zn levels than cultivated rice, O. sativa Nipponbare, and identified responsible genomic loci. An increase in grain Zn levels caused by one of the loci, qGZn9a, is associated with fertility reduction, but how this negative effect on grain productivity is regulated remains unknown. In this study, we artificially trimmed spikelets on the flowering day and found that a reduction in number of seeds was associated with an increase in the grain Zn levels. We also found that a partial defect in anther dehiscence correlated with the increase in grain Zn levels in plants carrying the W1627 chromosomal segment at qGZn9a in a Nipponbare genetic background. Among eight candidate genes in the qGZn9a region, three were absent from the corresponding region of W1627; one of these, Os09g0384900, encoding a DUF295 protein with an unknown function, was found to be specifically expressed in the developing anther, thereby suggesting that the gene may be involved in the regulation of anther dehiscence. As fertility and grain Zn levels are essential agronomic traits in rice, our results highlight the importance of balancing these two traits.

See: https://link.springer.com/article/10.1007/s00122-021-03873-4

Figure 4: Candidate genes at qGZn9a. a Candidate region of qGZn9a on chromosome 9. The positions of eight genes are displayed below the chromosome based on the Rice Annotation Project Database. Grey-coloured genes are missing in the corresponding region of qGZn9a in W1627. b Grain Zn concentration of two Tos17-inserted mutants, NC0405, the insertion on Os09g0382300, and ND4542, the insertion on Os09g0383300, were obtained. Data are mean ± SD of 4 and 6 plants for NC0405 and ND4542 compared with Nipponbare wild-type control in 2014 and 2020, respectively. n.s. indicates no significance by unpaired Student’s t test.