11-02-2013, 03:38 PM
Narrowing down the targets for yield improvement in rice under normal and abiotic stress conditions via expression profiling of yield-related genes
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Abstract
Background: Crop improvement targeting high yield and tolerance to environmental stresses has become the
need of the hour. Yield improvement via breeding or gene pyramiding aiming comprehensive incorporation of the
agronomically favored traits requires an in-depth understanding of the molecular basis of these traits. The present
study describes expression profiling of yield-related genes in rice with respect to different developmental stages
and various abiotic stress conditions.
Results: Our analysis indicates developmental regulation of the yield-related genes pertaining to the genetic
reprogramming involved at the corresponding developmental stage. The gene expression data can be utilized to
specifically select particular genes which can potentially function synergistically for enhancing the yield while
maintaining the source-sink balance. Furthermore, to gain some insights into the molecular basis of yield penalty
during various abiotic stresses, the expression of selected yield-related genes has also been analyzed by qRT-PCR
under such stress conditions. Our analysis clearly showed a tight transcriptional regulation of a few of these
yield-related genes by abiotic stresses. The stress-responsive expression patterns of these genes could explain some
of the most important stress-related physiological manifestations such as reduced tillering, smaller panicles and
early completion of the life cycle owing to reduced duration of vegetative and reproductive phases.
Background
Rice is one of the most important staple food crops feeding
almost half of the world population. There are many
reasons for the growing concern about sustainable and sufficient
production of various staple food crops including
rice. Some of these are the ever-increasing population, less
availability of arable land, global climate changes and
decreasing availability of water for agriculture (Takeda and
Matsuoka, 2008). In order to support the growing human
population, a more sustainable means of rice production is
needed. Specifically, crop improvement targeting high-yield
and enhanced tolerance to various environmental stresses
has become an urgent necessity.
Being a complex trait, grain yield in rice is determined
by the three component traits viz. grain number per
panicle, grain weight, and number of panicles per plant
(Xing and Zhang, 2010).
Developmental regulation of genes affecting tillering
process
Number of tillers determine the number of panicles per
plant and hence the number of grains. Tillering requires
the fine-tuning of expression of many genes such as
MOC1 (Li et al. 2003), LRK1 (Zha et al. 2009), OsTB1
(Takeda et al. 2003), D10 (Arite et al. 2007), Htd1 (Zou
et al. 2006), and D3 (Ishikawa et al. 2005). Amongst
these, MOC1 and LRK1 promote the formation of tillers
whilst others function as negative regulators. In our analysis
of the expression of the above genes, we found that
LRK1 is expressed more at the seedling and tillering
stages; whereas OsTB1 had very low expression level at
these stages (Figure 2D). In case of other negative regulators,
the expression data could not explain any defined
pattern of regulation (Figure 2D).