Fiziološki i morfološki efekti ekspresije AtCKX gena u transformisanim biljkama krompira (Solanum tuberosum L.) gajenim in vitro
Physiological and morphological effects of expression of AtcKX genes in transformed potato (Solanum tuberosum l.) plants grown in vitro
Abstract:
Potato (Solanum tuberosum L.) is the world's fourth most important food
crop. Its economical importance arises from its potential to develop tubers, edible
storage organs derived from modified underground lateral shoots, which
accumulate starch. Extensive research has provided evidence that plant hormones
cytokinins have an important role in control of tuberization. Cytokinin
oxidase/dehydrogenase (CKX) is the key enzyme of cytokinin catabolism in
plants, thus transgenic plants expressing CKX genes have provided a valuable
model system for the research of cytokinin homeostasis. Potato (cv. "Désirée")
plants have been transformed with AtCKX1 and AtCKX2 genes from Arabidopsis
thaliana, in order to determine the effects of altered cytokinin homeostasis on the
morphological and physiological features of the transformed potato plants grown
in vitro, with particular emphasis on the tuberization process. A high level of
transgene expression and/or CKX activity in shoots and roots have been
confirmed in two AtCKX1 and three AtCKX2 lines. The expression of AtCKX genes
has reflected on significant changes in the hormonal homeostasis of the
transformed potato plants grown in vitro, but did not lead to the decrease of total
endogenous cytokinin levels. However in the majority of the AtCKX lines, the
levels of bioactive cytokinins (nucleobases and ribosides), as well as cytokinin
nucleotides, were significantly decreased. In addition, the level of endogenous
indole-3-acetic acid (IAA) was also significantly changed. The altered hormonal
homeostasis reflected on the morphological level, including the tuberization
process. Tuberization was altered in AtCKX potato lines both in long-day
conditions, and in continuous darkness. In three of the five AtCKX lines, the
overcoming of the inhibitory effect of light on tuber induction has been observed.
In these lines, tubers appeared already during the first 30 days in long-day
conditions, which has never been observed in control plants of this potato cultivar.
The AtCKX plants developed less tubers per shoot in comparison to control plants,
indicating decreased tuber initiation in plants with lower endogenous levels of
bioactive cytokinins. It is possible that this was a consequence of the increased
ratio of IAA vs. bioactive cytokinins. The effect on tuber initiation was more
pronounced in continuous darkness, than in long-day conditions. Tuber diameter
and mass did not significantly differ from control values in the majority of
transformed AtCKX lines. Only one of the five transformed lines, AtCKX1-36a
developed tubers of smaller diameter and mass. Cytokinins have different effects
on particular steps in the tuberization process in potato. Lower bioactive cytokinin
levels lead to early tuber induction in AtCKX plants, but this effect is not followed
by enhanced tuber initiation and growth. Further research on potato plants that
would express either cytokinin catabolism (AtCKX) or biosynthesis (ipt)
transgenes, is required to identify the regulation mechanisms by which cytokinins
affect particular steps of the tuberization process in both tuber-inducing and noninducing
conditions.
Keywords:
Bioactive cytokinins; Cytokinin oxidase/dehydrogenase (CKX); Genetictransformation; Genetic engineering; In vitro; Potato (Solanum tuberosum L. cv.Désirée); Transgene; TuberizationSource:
University of Belgrade, Faculty of Biology, 2013, 1-206URI
http://eteze.bg.ac.rs/application/showtheses?thesesId=1090https://fedorabg.bg.ac.rs/fedora/get/o:7796/bdef:Content/download
http://vbs.rs/scripts/cobiss?command=DISPLAY&base=70036&RID=45152015
http://nardus.mpn.gov.rs/123456789/2152
https://radar.ibiss.bg.ac.rs/handle/123456789/2411