miRNA-Mediated Regulation of Germination

Guo et al. show that miR9678 affects seed germination in wheat by generating phased siRNAs and modulating abscisic acid/gibberellin signaling. Plant Cell https://doi.org/10.1105/tpc.17.00842

By Guanghui Guo and Yingyin Yao

Background:  Seed germination is important for grain yield and quality and rapid, near-simultaneous germination in a crop helps in cultivation; however, cultivars that germinate too readily can undergo pre-harvest sprouting, which causes substantial losses in areas that tend to get rain around harvest time. Moreover, knowledge of the mechanisms regulating seed germination in wheat remain limited. Micro RNAs (miRNAs) are known to regulate the expression of many genes, and the wheat-specific miRNA miR9678 is specifically expressed in the scutellum of developing and germinating seeds.

Question: Does miR9678 have a function during seed germination and how does it work?

Findings: We provided evidence that miR9678 targets a long non-coding RNA (WSGAR) and triggers the generation of phased small interfering RNA (phasiRNA) that play a role in the delay of seed germination. Overexpression of miR9678 delays germination and helps prevent pre-harvest sprouting in wheat through reducing bioactive gibberellin levels, wherease silencing of miR9678 enhances germination rates. We also show that abscisic acid signaling proteins bind the promoter of the miR9678 precursor and activate its expression, indicating that miR9678 affects germination by modulating both gibberellin and abscisic acid signaling.

Next steps: Although our findings provide solid support that miR9678-WSGAR-phasiRNAs affect seed germination, further work is required to fully elucidate the underlying mechanisms, including the possible use of a scutellum specific promoter, the production of null miR9678 mutants, along with the development of new techniques for the characterization of target genes.

Guanghui Guo, Xinye Liu, Fenglong Sun, Jie Cao, Na Huo, Bala Wuda, Mingming Xin, Zhaorong Hu, Jinkun Du, Rui Xia, Vincenzo Rossi, Huiru Peng, Zhongfu Ni, Qixin Sun, Yingyin Yao. (2018). Wheat miR9678 affects seed germination by generating phased siRNAs and modulating abscisic acid/gibberellin signaling. Plant Cell Apr 2018, 30: 796-814; DOI: https://doi.org/10.1105/tpc.17.00842