Identification and Analyses of Genes Differentially Expressed During Grain Filling in Indica Rice (Oryza Sativa L.) Variety Mr 84
Rice is one of the major crops in Malaysia. It has been a staple food of the Malaysian community for many decades. Continued growth of Malaysian population put additional pressure on local rice production to meet the demand of the consumption. Rice grain filling is a critical factor that directly...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2006
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/186/1/549027_FBSB_2006_8.pdf |
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| Summary: | Rice is one of the major crops in Malaysia. It has been a staple food of the
Malaysian community for many decades. Continued growth of Malaysian
population put additional pressure on local rice production to meet the
demand of the consumption. Rice grain filling is a critical factor that directly
affects the local rice production. This preliminary study was carried out to
identify genes that are putatively involved in the grain filling of rice by using
cDNA subtraction. Four subtracted cDNA libraries were constructed from
three different pools of RNA (samples A, B and C) during the reproductive
and ripening phase of rice. A total of 2366 clones were obtained from these
four subtracted cDNA libraries and 384 clones were sequenced. In sample A
(panicle initiation), most of the sequenced cDNA were putatively involved in
cell wall structure and metabolism (38 %) e.g. pollen allergen (subtraction 1).
The number of putative genes involved in metabolism (9 %) and storage
protein (3 %) was low in this library (subtraction 1). The genes that were
differentially expressed in heading to milk stage (sample B) were mainly involved in metabolism (28 %, subtraction 3). Most of the genes that were
differentially expressed in sample C (milk stage to maturation) were putative
storage proteins (61 %) e.g. glutelins and prolamins, and the genes that were
putatively involved in metabolism (10 %) decreased compared to subtraction
3. This reflected that metabolic activities in panicles significantly reduced and
most of the activities in grain were involved in reserving food towards the end
of the grain filling. To understand the grain filling process during rice growth
stages, ADP-glucose pyrophosphorylase which is the rate-limiting enzyme in
starch biosynthesis was studied. The cDNA for the 3’ region of ADP-glucose
pyrophosphorylase small subunit (Adp3’-2) (which showed 97 % identity to
ADP-glucose pyrophosphorylase small subunit from japonica cultivar) was
isolated. It was preferentially expressed in milk and dough stage of grain
development. Southern analysis showed that Adp3’-2 may be a single copy
gene in the rice genome. In addition, bZIP protein which has a regulatory role
in several plant developmental processes including seed storage has also
been cloned. The cDNA for the 3’ region of bZIP protein was also isolated.
No signal was detected in Northern analysis attributed to its low expression in
panicle, and the Southern analysis also suggested that 3’ Reb-2 may be a
single copy gene in the rice genome |
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