Small and round seed 5gene encodes alpha-tubulin regulating seed cell elongation in rice

Segami Shuhei, Kono Izumi, Ando Tsuyu, Yano Masahiro, Kitano Hidemi, Miura Kotaro, Iwasaki, Iwasaki Yukimoto

Description

Seed size is an important trait in determinant of rice seed quality and yield. In this study, we report a novel semi-dominant mutant S mall and r ound s eed 5 ( Srs5 ) that encodes alpha-tubulin protein. Lemma cell length was reduced in Srs5 compared with that of the wild-type. Mutants defective in the G-protein alpha subunit ( d1-1 ) and brassinosteroid receptor, BRI1 ( d61-2 ) also exhibited short seed phenotypes, the former due to impaired cell numbers and the latter due to impaired cell length. Seeds of the double mutant of Srs5 and d61-2 were smaller than those of Srs5 or d61-2 . Furthermore, SRS5 and BRI1 genes were highly expressed in Srs5 and d61-2 mutants. These data indicate that SRS5 independently regulates cell elongation of the brassinosteroid signal transduction pathway

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 0
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Segamiet al.Rice2012,5:4 http://www.thericejournal.com/content/5/1/4

R E S E A R C HOpen Access Small and round seed 5gene encodes alpha tubulin regulating seed cell elongation in rice 1 2,32,4 56 1* Shuhei Segami , Izumi Kono, Tsuyu Ando, Masahiro Yano , Hidemi Kitano , Kotaro Miuraand 1* Yukimoto Iwasaki

Abstract Seed size is an important trait in determinant of rice seed quality and yield. In this study, we report a novel semi dominant mutantSmall and round seed 5(Srs5) that encodes alphatubulin protein. Lemma cell length was reduced inSrs5compared with that of the wildtype. Mutants defective in the Gprotein alpha subunit (d11) and brassinosteroid receptor, BRI1 (d612) also exhibited short seed phenotypes, the former due to impaired cell numbers and the latter due to impaired cell length. Seeds of the double mutant ofSrs5andd612were smaller than those ofSrs5ord612. Furthermore,SRS5andBRI1genes were highly expressed inSrs5andd612mutants. These data indicate thatSRS5independently regulates cell elongation of the brassinosteroid signal transduction pathway

Background Seed size and weight are important traits for rice yield (Song and Ashikari 2008, Takeda and Matsuoka 2008). Several quantitative trait loci (QTLs) affecting seed size have been identified, namelyGW2encoding a RING type protein that functions as an E3 ubiquitin ligase (Songet al. 2007),qSW5encoding a novel protein with no known domains (Shoumuraet al. 2008), andGS3 encoding a membrane protein with various conserved domains (Fanet al. 2006, TakanoKaiet al. 2009). Loss ofGW2andqSW5function leads to a wider seed phe notype, and loss ofGS3function leads to a longer seed phenotype, both resulting in increased yield. Causal genes of the small (or short) seed mutants have also been identified, namelyd1(also namedRGA1) encoding the heterotrimeric G protein alpha subunit (Ashikariet al. 1999, Fujisawaet al. 1999),d11encoding a cytochrome P450 involved in brassinosteroid (BR) bio synthesis (Tanabeet al. 2005),d2andbrd2encoding another type of cytochrome P450 involved in BR synth esis (Hong et al. 2003, Honget al. 2005),d61(also namedOsBRI1) encoding the BR receptor (Yamamuro et al. 2000),srs1encoding a novel protein that has no known functional domains (Abeet al. 2010), and finally,

* Correspondence: miura[e-mail]; [e-mail] 1 Faculty of Biotechnology, Fukui Prefectural University, 411 Kenjojima, Matsuoka, EiheijiTown, Fukui 9101195, Japan Full list of author information is available at the end of the article

srs3encoding a kinesin 13 protein (Kitagawaet al. 2010). During seed formation in rice, it was demon strated thatD1regulates cell number (Izawaet al. 2010), andSRS1andSRS3regulate cell length (Abe et al. 2010, Kitagawaet al. 2010). From these observa tions,SRS1andSRS3seem to affect seed size through signaling pathways other than Gprotein signal transduction. Although several genes regulating seed size have been identified, their molecular network underlying seed for mation remains unclear. Here we report molecular clon ing of a novel small and round seed mutant inSrs5 ( Small and round seed 5). The results clearly demon strated thatSrs5encodes alphatubulin and regulates cell elongation in rice seed.

Results Characterization of theSrs5mutant A mutant line, Kyudai No. 37, was identified by screen ing of small or short seed mutants from the rice collec tions of Togo Field, Nagoya University, and renamed Small and round seed 5, (Srs5).Srs5shows shorter and rounder seeds, a shorter panicle and semidwarf plant phenotype, compared to WT (Figure 1AC). Addition ally, F 1 plants derived from a cross between WT and Srs5plants show intermediate seed length of parents seeds (Figure 1A and 1D). From these results, we pre sumed that theSrs5mutation acts as semidominant

© 2012 Segami et al; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.