Abstract
The maize brachytic2 (br2) gene encodes a protein homologous to the Arabidopsis ABCB1 protein, which actively transports chemically diverse substrates across cellular membranes. This includes indole-3-acetic acid (IAA), the most abundant natural form of auxin, a key regulator of plant growth and tropisms. Defects in auxin transport are responsible for the short stature of br2 mutants. We describe a novel br2 mutant allele present in NC238, an inbred maize of medium stature and demonstrate that the mutant allele br2-NC238 is caused by the insertion of a novel transposon in intron IV of the br2 gene. A tall revertant of NC238 (NC238-rev) appeared spontaneously as a result of excision of the transposon from the br2 gene. This event yielded two completely isogenic versions of the NC238 inbred, one brachytic (NC238-ref) and one tall (NC238-rev). The presence of the transposon in br2-NC238 alters normal splicing of the transcript, producing several splicing forms. One splicing form, ABCB1-T02, was abundantly expressed in NC238-ref, while its expression was very weak in tall NC238-rev plants. Differences between NC238-rev and NC238-ref were also detected in the expression pattern of auxin transporter genes. Morphological changes associated with the br2-NC238 mutant allele included reduced length and increased diameter of the lower internodes. The shortening of plant stature was confirmed in the B73 genetic background by introgression of the br2-NC238. Our results demonstrate that br2-NC238 reduces plant height without altering other morphological traits, and might thus be useful in maize breeding programs when reduction of stature is desired.
Similar content being viewed by others
Abbreviations
- ABCB:
-
Adenosine triphosphate ATP-binding cassette transporter
- Br:
-
Brachytic
- BUM:
-
2-[4-(Diethylamino)-2-hydroxybenzoyl] benzoic acid
- MITE:
-
Miniature inverted-repeat transposon elements
- NAA:
-
1-Naphthaleneacetic acid
- NPA:
-
1-N-naphthylphthalamicacid
- PAT:
-
Polar auxin transport
- PCIP:
-
p-chlorophenoxyisobutyric acid
- RAI:
-
Root Area Index
- RSD:
-
Root surface density
- Zm:
-
Zea mays L
References
Ambudkar SV, Kimchi-Sarfaty C, Sauna ZE, Gottesman MM (2003) P-glycoprotein: from genomics to mechanism. Oncogene 22:7468–7485
Bailly A, Yang H, Martinoia E, Geisler M, Murphy AS (2011) Plant lessons: exploring ABCB functionality through structural modeling. Front Plant Sci 2:108
Balzan S, Johal GS, Carraro N (2014) The role of auxin transporters in monocots development. Front Plant Sci 5:393
Bengough AG (2005) Root responses to soil physical conditions; growth dynamics from field to cell. J Exp Bot 57:437–447
Blilou I, Xu J, Wildwater M, Willemsen V, Paponov I, Friml J, Heidstra R, Aida M, Palme K, Scheres B (2005) The PIN auxin efflux facilitator network controls growth and patterning in Arabidopsis roots. Nature 433:39–44
Carraro N, Forestan C, Canova S, Traas J, Varotto S (2006) ZmPIN1a and ZmPIN1b encode two novel putative candidates for polar auxin transport and plant architecture determination of maize. Plant Physiol 142:254–264
Casacuberta JM, Santiago N (2003) Plant LTR-retrotransposons and MITEs: control of transposition and impact on the evolution of plant genes and genomes. Gene 311:1–11
Castelletti S, Tuberosa R, Pindo M, Salvi S (2014) A MITE transposon insertion is associated with differential methylation at the maize flowering time QTL Vgt1. G3 4:805–812
Cho M, Cho H-T (2013) The function of ABCB transporters in auxin transport. Plant Signal Behav 8:e22990
Fedoroff N (2000) Transposons and genome evolution in plants. Proc Natl Acad Sci USA 97:7002–7007
Feschotte C, Jiang N, Wessler SR (2002) Plant transposable elements: where genetics meets genomics. Nat Rev Genet 3:329–341
Forestan C, Farinati S, Varotto S (2012) The maize PIN gene family of auxin transporters. Front Plant Sci 3:16
Gallavotti A (2013) The role of auxin in shaping shoot architecture. J Exp Bot 64:2593–2608
Gallavotti A, Yang Y, Schmidt RJ, Jackson D (2008) The relationship between auxin transport and maize branching. Plant Physiol 147:1913–1923
Galli M, Liu Q, Moss BL, Malcomber S, Li W, Gaines C, Federici S, Roshkovan J, Meeley R, Nemhauser JL, Gallavotti A (2015) Auxin signaling modules regulate maize inflorescence architecture. Proc Natl Acad Sci USA 112:13372–13377
Geisler M, Murphy AS (2006) The ABC of auxin transport: the role of p-glycoproteins in plant development. FEBS Lett 580:1094–10102
Hedden P (2003) The genes of the Green Revolution. Trends Genet 19:5–9
Higgins CF, Linton KJ (2004) The ATP switch model for ABC transporters. Nat Struct Mol Biol 11:918–926
Jasinski M, Ducos E, Martinoia E, Boutry M (2003) The ATP-binding cassette transporters: Structure, function, and gene family comparison between. Plant Physiol 131:1169–1177
Kang J, Park J, Choi H, Burla B, Kretzschmar T, Lee Y, Martinoia E (2011) Plant ABC transporters. Arab B 9:e0153
Khush GS (2001) Green revolution: the way forward. Nat Rev Genet 2:815–822
Knöller AS, Blakeslee JJ, Richards EL, Peer WA, Murphy AS (2010) Brachytic2/ZmABCB1 functions in IAA export from intercalary meristems. J Exp Bot 61:3689–3696
Multani DS, Briggs SP, Chamberlin M, Blakeslee JJ, Murphy AS, Johal GS (2003) Loss of an MDR transporter in compact stalks of maize br2 and sorghum dw3 mutants. Science 302:81–84
Petersen G, Seberg O (1999) Phylogenetic evidence for excision of stowaway miniature inverted-repeat transposable elements in Triticeae (Poaceae). Mol Biol Evol 17:1589–1596
Pilu R, Cassani E, Villa D, Curiale S, Panzeri D, Badone FC, Landoni M (2007) Isolation and characterization of a new mutant allele of brachytic 2 maize gene. Mol Breed 20:83–91
Reinhardt D, Pesce E-R, Stieger P, Mandel T, Baltensperger K, Bennett M, Traas J, Friml J, Kuhlemeier C (2003) Regulation of phyllotaxis by polar auxin transport. Nature 426:255–260
Sampath P, Yang T-J (2014) Miniature inverted-repeat transposable elements (MITEs) as valuable genomic resources for the evolution and breeding of Brassica crops. Plant Breed Biotech 2:322–333
Scheres B, Xu J (2006) Polar auxin transport and patterning: grow with the flow. Genes Dev 20:922–926
Varagona MJ, Purugganan M, Wessler SR (1992) Alternative splicing induced by insertion of retrotransposons into the maize waxy gene. Plant Cell 4:811–820
Xing A, Gao Y, Ye L, Zhang W, Cai L, Ching A, Llaca V, Johnson B, Liu L, Yang X et al (2015) A rare SNP mutation in Brachytic2 moderately reduces plant height and increases yield potential in maize. J Exp Bot 66:3791–3802
Yang H, Murphy AS (2009) Functional expression and characterization of Arabidopsis ABCB, AUX 1 and PIN auxin transporters in Schizosaccharomyces pombe. Plant J 59:179–191
Zazímalová E, Murphy AS, Yang H, Hoyerová K, Hosek P (2010) Auxin transporters–why so many? Cold Spring Harb Perspect Biol 2:1–14
Acknowledgements
We thank Prof. Teofilo Vamerali (DAFNAE University of Padova) for help in root measurements and data analyses, Profs. Johal and Varotto lab members for help in field and greenhouse work and Alison Garside for English revision.
Author information
Authors and Affiliations
Contributions
This study was a collaboration between University of Padova (Italy) and Purdue University (U.S.A.). SB and NC conducted the experiments. BS did much of the initial work characterizing the br2-NC238 mutant allele and its tall revertant. SB and CDC performed root system measurements and analysis. MRT produced the introgression into B73 and generated NILs of B73 containing and lacking the br2-NC238. SV and GJ conceived the project and obtained funds to support it. GJ, SV, SB and NC analyzed the data and wrote the manuscript. All authors have read and approved the final manuscript.
Corresponding author
Electronic supplementary material
Below is the link to the electronic supplementary material.
10725_2018_412_MOESM1_ESM.jpg
Supplementary Fig. 1 Measurements of root traits of NC238 (dark grey) and NC238-rev (light grey) at flowering stage. (A) RLD profile of NC238 and NC238-rev in ten soil horizons. For both lines, the RLD profile was higher in the top 40 cm of soil depth and then formed a plateau. (B) The RDL average of NC238 and NC238-rev did not differ significantly. (C) The root diameter of the two lines was similar in each of the ten soil horizons, with thinner roots in the deeper cores. (D) The RSD profile of NC238 and NC238-rev in ten soil horizons was similar, with a decrement from the 40 cm depth. (E) The average RAI of NC238 and NC238-rev in ten soil horizons: data did not show statistically significant differences—Supplementary material 1 (JPG 110 KB)
10725_2018_412_MOESM2_ESM.jpg
Supplementary Fig. 2 Effects of auxin analogs and PAT inhibitors on seedlings growth of NC238 and NC238-rev 10 µM NAA causes proliferation and elongation of seminal roots, lateral roots and root hairs in both NC238-rev (A) and NC238 (B) lines, compared to the mock treatments with NaOH (mock solution) in NC238-rev (C) and NC238 (D). 50 µM NPA application causes gravitropic defects in seminal and primary roots in NC238-rev (E) and NC238 (F) compared to DMSO treatments (mock solution) in NC238-rev (G) and NC238 (H) seedlings. Scale (black bar) = 1 cm—Supplementary material 2 (JPG 138 KB)
Rights and permissions
About this article
Cite this article
Balzan, S., Carraro, N., Salleres, B. et al. Genetic and phenotypic characterization of a novel brachytic2 allele of maize. Plant Growth Regul 86, 81–92 (2018). https://doi.org/10.1007/s10725-018-0412-6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10725-018-0412-6