The research in our lab is centered on the developmental processes and signaling events associated plant reproduction. Our main focus currently is on the heteromorphic self-incompatibility (HSI) system in Primula vulgaris (Primrose). HSI promotes out-breeding by combining a set of morphological characteristics that differ between mating types, with a physiological recognition system. In Primula there are two floral mating types, which exhibit reciprocally positioned male and female organ, the anthers and stigma. Pollen number and size, and the size and shape of stigmatic and stylar cells also differ between morphs, and these characters act synergistically to promote out-crossing, whilst a biochemical recognition system prevents pollen from the same mating type effecting fertilization. HSI is controlled by a diallelic S-locus, the short style (thrum) morph is determined by the dominant S allele being Ss in genotype and the long styled (pin) morph is homozygous recessive (ss).
Traditional genetic studies have suggested that this S-locus is in fact a supergene – a number of tightly linked genes with the alleles of at least 7 loci linked and inherited as a single unit. Identification and characterization of the genes which make up the supergene has the potential to make a significant impact of our understanding of floral biology, not just in the functioning and evolution of HSI systems, but also in the regulation of floral morphology (cell size and shape) and male reproductive capacity (pollen number). We are combining transcriptomic approaches to identify genes that are differentially expressed in floral tissues of the two mating types, with identifying and sequencing genomic clones linked to the S-locus to unravel the molecular basis of this breeding system.
This project offers an opportunity to study several key aspects of plant reproductive biology and promises to provide new insights into the evolution and control of plant breeding systems. In addition recent developments in the use of transgenic crops have led to concerns about the escape of transgenes into wild relatives. One way to address this problem would be to reproductively isolate crop species, studies such as this of the coordination of floral traits to produce breeding barriers will make a valuable contribution to achieving this goal.
Guo, F., Yoon G.M, and McCubbin, A.G. (2013) PiSCP1 and PiCDPK2 localize to peroxisomes and are involved in pollen tube growth in Petunia inflata. Plants 2, 72-86.
Guo F and McCubbin, A.G. (2012) The pollen specific R-SNARE/longin PiVAMP726 mediates fusion of endo- and exocytic compartments in pollen tube tip growth. J. Exp. Bot. 63: 3083-95.
McCubbin, A.G. (2008) Heteromorphic self-incompatibility in Primula: Twenty-first century tools promise to unravel a classic nineteenth century model system. In “Self-Incompatibility in Flowering Plants, evolution, diversity and mechanisms”. Ed. V. Franklin-Tong. Springer. Pp 286-308.
Hetrick, A. and McCubbin, A.G. (2007) Heteromorphy and Flower Development in Primula. International Journal of Plant Developmental Biology 1(1): 82-86.
Roalson E.H., McCubbin, A.G. and Whitkus, R. (2007) Chromosome Evolution in the Cyperales. Aliso 23: 62-71.
Yoon,G.M., Dowd, P.E., Gilroy,S. and McCubbin,A.G. (2006) Calcium-Dependent Protein Kinase isoforms have distinct functions in pollen tube growth, including regulating polarity. The Plant Cell 18: 867-878.
McCubbin, A.G., Lee, C., and Hetrick, A. (2006). Identification of genes showing differential expression between morphs in developing flowers of Primula vulgaris. Sexual Plant Reproduction 19: 51-62.
McCubbin, A.G. and Roalson, E.H. (2005) Construction of bacterial artificial chromosome libraries for use in phylogenetic studies. Methods in Enzymology 395: 384-399.
McCubbin, A.G. (2005) Lessons on signaling in plant self-incompatibility systems. In: “Intercellular Communication in Plants” (Annual Plant Review Series) Ed. A. Fleming. Blackwell Publishing: pp. 240-275.
McCubbin, A.G., Ritchie, S.M., Swanson, S.J. and Gilroy, S. (2004) The calcium-dependent protein kinase HvCDPK1 mediates the gibberellic acid response of the barley aleurone through regulation of vacuolar function. The Plant Journal 39:206-218.
Sijacic, P., Wang, X., Skirpan, A.L., Wang, Y., Dowd, P.E., McCubbin, A.G., Huang, S. and Kao, T.-h. (2004) Identification of the pollen determinant of S-RNase-mediated self-incompatibility. Nature 429: 302-305.
Wang, Y., Tsukamoto, T., Yi, K.-w., Wang, X., Huang, S., McCubbin, A.G. and Kao, T.-h. (2004) Chromosome walking in the Petunia inflata self-incompatibility (S-) locus and gene identification in an 881-kb contig containing S2-RNase. Plant Molecular Biology 54: 727-742.
Roalson E.H. and McCubbin A.G. (2003) S-RNases and sexual incompatibility: structure, functions, and evolutionary perspectives. Molecular Phylogenetics and Evolution 29: 490-506.