miR172 down-regulates the translation of cleistogamy 1 in barley

Authors: ANWAR, NADIA - National Institute Of Agrobiological Sciences (NIAS); OHTA, MASARU - National Institute Of Agrobiological Sciences (NIAS); YAZAWA, TAKAYUKI - National Institute Of Agrobiological Sciences (NIAS); SATO, YUTAKA - National Institute Of Agrobiological Sciences (NIAS); LI, CHAO - National Institute Of Agrobiological Sciences (NIAS); TAGIRI, AKEMI - National Institute Of Agrobiological Sciences (NIAS); SAKUMA, MARI - National Institute Of Agrobiological Sciences (NIAS); NUSSBAUMER, THOMAS - Institute For Bioinformatics - Germany; Bregitzer, Paul; POURKHEIRANDISH, MOHAMMAD - National Institute Of Agrobiological Sciences (NIAS); WU, JIANZHONG - National Institute Of Agrobiological Sciences (NIAS); KOMATSUDA, TAKAO - National Institute Of Agrobiological Sciences (NIAS)

Submitted to: Annals of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2018
Publication Date: 5/22/2018
Citation: Anwar, N., Ohta, M., Yazawa, T., Sato, Y., Li, C., Tagiri, A., Sakuma, M., Nussbaumer, T., Bregitzer, P.P., Pourkheirandish, M., Wu, J., Komatsuda, T. 2018. miR172 down-regulates the translation of cleistogamy 1 in barley. Annals Of Botany. https://doi.org/10.1093/aob/mcy058.
DOI: https://doi.org/10.1093/aob/mcy058

Interpretive Summary: Barley plants reproduce mainly through self-pollination, meaning that a they do not have to cross-pollinate with other plants to set seed. One type of flowering response, cleistogamy (meaning "closed"), occurs when barley florets remain closed at the time of pollination, making it difficult for pollen from other plants to enter. It also makes the spores of disease organisms, such as the one causing Fusarium head blight, unable to enter the flower and cause infection at that time. However, some barley varieties have florets that open during pollination. This can enable cross-pollination, which may be helpful for hybrid production but also make the plants more susceptible to Fusarium infection. This report, a continuation of many years of research, describes a detailed control mechanism involving two key genes that interact to influence open versus closed flowering in barley. A detailed knowledge of how genes work together to produce complex traits is helpful for practical applications (controlling access of pollen and spores to the inner parts of barley florets). More importantly, such studies contribute to the overall understanding of barley—and other higher plants we use for food—and gives geneticists and plant breeders information that can be used to make further improvements in plant yields and resistances to diseases.

Technical Abstract: Floret opening in barley is induced by the swelling of the lodicule, a trait under the control of the cleistogamy1 (cly1) gene. The product of cly1 is a member of the APETALA2 (AP2) transcription factor family, which inhibits lodicule development. A sequence polymorphism at the miR172 target site within cly1 has been associated with variation in lodicule development and hence with the cleistogamous phenotype. Here, an analysis of the small RNA content of the immature barley spike has revealed three isomers, miR172a, b and c, while miR172a was the most abundant. RNA in situ hybridization experiments have demonstrated that mature miR172 and cly1 mRNA co-localize in the lodicule primordium. The implication is that these two molecules potentially interact with one another. Immunoblot analysis showed that the sequence polymorphism at the miR172 target site within cly1 reduced the abundance of the CLY1 protein, but not that of its transcript. In a Ds-induced mutant of Hv-miR172a, which generates no mature miR172a, the lodicules fail to develop, resulting in a very small lodicule. Direct evidence is presented to show that miR172 acts to reduce the abundance of the CLY1 protein, which enables open-flowering in barley.