Molecular, genetic and phenotypic analysis of genes controlling lateral spikelet fertility in barley
Final Report Abstract
Inflorescence architecture of barley (Hordeum vulgare L.) is common among the Triticeae species, which bear one to three single-flowered spikelets at each rachis internode. Triple spikelet meristem (TSM) is one of the unique features of barley spikes, in which three spikelets (one central and two lateral spikelets) are produced at each rachis internode. Fertility of the lateral spikelets at TSM gives row-type identity to barley spikes. Six-rowed spikes show fertile lateral spikelets and produce increased grain yield per spike, compared to two-rowed spikes with sterile lateral spikelets. Thus far, two loci governing the row-type phenotype were isolated in barley that include Six-rowed spike1 (Vrs1) and Intermedium-C (Int-C). In the present study, we isolated Six-rowed spike4 (Vrs4), a barley ortholog of the maize (Zea mays L.) inflorescence architecture gene RAMOSA2 (RA2). Eighteen coding mutations in barley RA2 (HvRA2) were specifically associated with lateral spikelet fertility and loss of spikelet determinacy. Expression analyses through mRNA in situ hybridization and microarray showed that Vrs4 (HvRA2) controls the row-type pathway through Vrs1 (HvHox1), a negative regulator of lateral spikelet fertility in barley. Moreover, Vrs4 may also regulate transcripts of barley SISTER OF RAMOSA3 (HvSRA), a putative trehalose-6-phosphate phosphatase (T6PP), involved in T6P homeostasis implicated to control spikelet determinacy. Our expression data illustrated that although RA2 is conserved among different grass species, its down-stream target genes appear to be modified in barley and possibly other species of tribe Triticeae. Taken together, our results suggest that Vrs4 is a central player in establishing inflorescence architecture of barley spikes, as well as in determining yield potential and grain number. Thus, a better understanding of the underlying gene regulatory networks during spike formation may help to improve future grain yields of small grain cereals.
Publications
- (2013) Six-rowed spike4 (Vrs4) controls spikelet determinacy and row-type in barley. Proc Natl Acad Sci USA 110: 13198–13203
Koppolu, R., N. Anwar, S. Sakuma, A. Tagiri, U. Lundqvist, M. Pourkheirandish, T. Rutten, C. Seiler, A. Himmelbach, R. Ariyadasa, H.M. Youssef, N. Stein, N. Sreenivasulu, T. Komatsuda, T. Schnurbusch
(See online at https://doi.org/10.1073/pnas.1221950110) - Six-rowed spike 4 (Vrs4) regulates spike architecture and lateral spikelet fertility in barley (Hordeum vulgare L.); Halle (Saale), Universitäts- und Landesbibliothek Sachsen-Anhalt, Diss., 2014
Koppolu, R.
