Kültür Bitkilerinde Apomiksi Genlerinin Klonlanması

Abstract

Kültür bitkilerinin iyileştirilmesi amacıyla uygulanan birçok ıslah stratejisinde elde edilen ticari hibritler üstün özelliklerini genetik açılımlardan dolayı sonraki döllerde koruyamazlar. Apomiksi, ana bitki ile genetik olarak özdeş tohumlar oluşturmasına olanak sağlayan ve kültür bitkilerinde başarıldığı takdirde ticari hibritlerin klonal çoğaltımına izin veren bir üreme şeklidir. Eşeyli üreme mayoz geçirmiş gametlerin oluşumu ve çifte döllenmeyi gerektiren bir süreçtir. Fakat apomiksi sırasında bu adımlardan birçoğu ya atlanır ya da değiştirilmiştir. Apomiktik türlerde, erkek ve dişi gametlerde kromozom sayısı yarıya inmez (apomayoz) buna rağmen embriyo kesesi ve polen oluşumu devam eder. Ayrıca, apomayotik yumurta hücresi (2n) döllenme olmaksızın kendiliğinden embriyoyu oluşturur (partenogenez). Bu nedenle, apomiksi tohum aracılığı ile klonal çoğalmaya yol açar. Buna karşın, henüz apomiksi doğal apomiktik türlerden tarımı yapılan kültür bitkilerine melezleme yolu ile aktarım başarılamamıştır. Günümüzde bu konuda araştırmacılar iki farklı alanda çalışmalar yürütmektedir; doğal apomiktik bitki türlerinde sorumlu genleri belirlemek veya eşeyli üreme süreçlerini değiştiren düzenlenmeler sayesinde apomiksiyi oluşturmak. Bu derlemede, apomiksiyi kontrol eden genetik mekanizmalar üzerine bu güne kadar elde edilmiş sonuçlar tartışılmıştır.

Keywords

• Diplospori,Apospori,Sporofitik apomiksi,Klonal tohum eldesi,Apomayoz

Cloning Apomixis Genes in Crops

Abstract

Hybrid plants, produced by many breeding strategies for improvement of culture plants could not conserve their hybrid vigor within the next generations. Apomixis is a reproduction way which creates genetically identical seeds with the maternal plant and it will enable the clonal reproduction of hybrids when it is achieved in culture plants. Sexual reproduction is a process involves gametes formed by meiosis and double fertilization. However, in apomictic process, many of these steps are either bypassed or modified. In apomict species; chromosome number in male and female gametes are not reduced (apomeiosis), nevertheless embryo sac and pollen formation continues. Furthermore, the apomeiotic egg cell (2n) spontaneously forms the embryo (parthenogenesis). Therefore, apomixis leads to clonal reproduction by seeds. Although, introduction of apomixis from natural apomicts to culture plants haven’t been achieved by hybridization methods. Recently researchers have been working on this subject with two different strategies. In this review, the recent knowledge about the molecular mechanisms controlling apomixis are discussed.

Keywords

• Diplospory,Apospory,Sporophytic apomixis,Apomeiosis,Clonal seed production

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