Theor Appl Genet (1998) 97: 135—140 ( Springer-Verlag 1998A. D. Deshpande · W. RamakrishnaG. P. Mulay · V. S. Gupta · P. K. RanjekarEvolutionary and polymorphic organization of the knotted1 homeobox in cerealsReceived: 17 October 1997 / Accepted: 9 December 1997Abstract Homeobox genes are the master controlgenes harbouring the homeobox which is crucial fordevelopmental associated functions. One homeoboxgene, knotted1, which has a role in leaf development, isconserved in plants and might have arisen from a singleancestral gene. Using PCR, we identif i ed multiple kn1homeoboxes in diverse cereals and showed a cereal/species-specif i c organization correlating them to evolu-tionary changes. We postulate the insertion of a largeintron preceded by duplication of the kn1 homeobox inthe lineage leading to rice.Key words Homeobox · Intron · Cereals ·Phylogeny · AncestryIntroductionThe homeobox was f i rst identif i ed in Drosophila(McGinnis et al. 1984) and later in several genes thatare involved in development in diverse groups of ani-mals and plants (Gehring, 1987). Dif f erent homeo-domains recognize diverse DNA binding sites and actas transcription factors (Scott et al. 1989). The thirdhelix (recognition helix) and the amino terminal regionof the homeodomainare very important in determiningthe specif i city of DNA binding (Triesman et al. 1989;Af f olter, 1990). The f i rst family of homeobox genesreported in plant species was the knotted1 (kn1) inCommunicated by P. M. A. TigerstedtA. D. Deshpande1 · W. Ramakrishna1 · G. P. MulayV. S. Gupta · P. K. Ranjekar ( )Plant Molecular Biology Unit, Division of Biochemical Sciences,National Chemical Laboratory, Pune - 411008, IndiaFax: 91-212-338234E-mail: bio@ems.ncl.res.in1Both of these authors have contributed equally to this papermaize which is involved in leaf development (Hakeet al. 1989; Vollbrecht et al. 1991). Kn1-like homeoboxgenes have recently been reported in other monocots,such as rice (Matsuoka et al. 1993) and barley (Mulleret al. 1995), and several dicot species such as Arabidop-sis (Lincoln et al. 1994), tomato (Hareven et al. 1996)and soybean (Ma et al. 1994). The knotted1 genes mayalso have a role in f l ower development as shown bytheir expression in the f l owers of rice (Tamaoki et al.1996). Intron duplication in the kn1 homeobox is asso-ciated with the conversion of the awned phenotype tothe hooded phenotype of seed in barley (Muller et al.1995).Sequence similarity of the homeobox in kn1-likegenes across monocot and dicot plant species suggestsa functional signif i cance that is conserved over avast evolutionary time scale (Vollbrecht et al. 1993).Genetic studies have shown that many of these genesare organized into regulatory gene families thatare related to each other by descent from a commonancestral gene. Homeobox genes should, therefore,prove to be useful in studying evolutionary changes inplants.In the study presented here, we show the dif f erentialorganization of the kn1 homeobox in diverse cereals,revealing the presence of multiple kn1 homologues,their crop/species-specif i c organization and variationsin intronic lengths, and we correlate them to cerealevolution.Materials and methodsPlant materialSeeds of oat, barley, wheat and rye and their respective wild rela-tives were obtained from USDA-ARS, National Small Grains Col-lection, Aberdeen, USA, and those of barley were obtained from theSwedish Agricultural University, Sweden. Seeds of the remainingcereals were obtained from various agricultural research stations inIndia.
