Kültür Bitkilerinde Apomiksi Genlerinin Klonlanması

Yıl 2017, Cilt: 10 Sayı: 1, 38 - 67, 28.06.2017

Kemal Melik Taşkın

Öz

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.

Anahtar Kelimeler

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

Cloning Apomixis Genes in Crops

Öz

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.

Anahtar Kelimeler

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

Kaynakça

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