Chapter 5 Genetic Analysis of Apomixis - cimmyt

238 T1tonoas Dr......... Joino G. 'arJnlIlI, aod Yv.. S.vidaobeen investigated in plants (e.g., Kinoshita etal. 1999; Vielle-Calzada et aI. 2000; Allemanand Doctor 2000; Crane, Chap. 3), but we arejust beginning to understand the molecularmechanisms underlying these processes.Nevertheless, the combination of maternalhypomethylation in combination with a lossof fie function was recently shown to enablethe formation of differentiated endospermwithout fertilization in Arabidopsis (Vinkenooget aI. 2000). It remains to be demonstratedwhether this approach is also feasible forcrops, especially cereals, but it represents apromising step in assembling the manycomponents needed to engineer apomixis intosexual crops.Another obstacle that needs to be overcome isthe relatively high number of genes/promoters that are required; in addition toinducible/repressible systems, it is likely thatthe precise and controlled interaction of manygenes will have to be engineered. In naturalapomicts, genes from different chromosomesare required for the expression of apomicticreproduction pathways. Blakey et aI. (1997)have shown that in apomictic Tripsacum, genesrequired for seed set are located on at least fiveTripsacum linkage groups, which are syntenicto four maize chromosome arms. Sherwood(Chap. 5) observes that the expression ofapospory requires the dominant allele of amajor gene or linkat and that the degree ofapomixis may be further influenced by manyother genes (e.g., modifiers). Fewer data areavailable for diplospory, but in this case aswell, a single master gene or a number ofgenesthat behave as a single locus may be requiredfor the expression of apomixis. The technicaldifficulties of introducing multipl~ geneswithin a single transformation event weresuccessfully resolved recently usingAgrobacterium-transformation with rice (Ye etaI. 20(0). Four genes were integrated on oneconstruct; by crossing transgenic lines carryingother transgenes, a whole biosyntheticpathway was engineered into rice endosperm(Ye et aI. 2(00).To sum up, our understanding of themolecular regulation of apomictic andamphimictic reproduction pathways in crops,especially cereals, is still in its infancy, and thus,due to the complexity of these biologicalprocesses, modifying or controlling thepathways will probably not be achievedwithin the next five years.Intellectual Property RightsIntellectual property rights (IPR) are a meansof promoting commercially relevantinnovation and for sharing resources. The IPRowner obtains the right to use the intellectualproperty (IP) exclusively, license it, or not useit at all for a limited period (e.g., 20 years). Inagricultural biotechnology and plant breeding,both scientific knowledge and its commercialapplications are increasingly being claimed bycompanies, but also by public institutions suchas universities and research centers (Spillane1999). With hundreds of millions of dollarsinvested every year in plant biotechnology andbreeding research, companies need effectiveIP protection to provide an incentive forniaking large research investments. Theseresearch results offer enormous benefits foragrochemical and seed companies, farmers,and the society as a whole. In the United States,cIPR include (i) geperal utility patents, (ii) PlantVariety Protection (UPGV), and (iii) plantpatents for asexually repro.duced plantsUondle 1999).Given this context, it is not surprising that IPRfor methods and .genes/promoters that areuseful for the genetic engineering of apomixishave been claimed (Table 14.2). Most of thepatents were filed during the last five years,probably because of improvements in plaJiltgene technology and in recognition of theenormous economic potential of utilizing