Chemistry Reference
In-Depth Information
Working on other phosphatases like PP1, we find data in
Vicia faba
studies supporting its
involvement in stomatal opening during the response to blue light (Takemiya et al. 2006). As
to PP2A, five genes encoding its catalytic subunit has been identified in rice, and three of
them show expression alteration under abiotic stress (Yu et al. 2003, 2005). And the activity
of PP2B needs the help from calcium (Luan 2003). Some others like DSP4, a dual-specificity
phosphatase, has been demonstrated to bind starch and interact with AKIN11, a SNF 1-
related kinase in Arabidopsis (Fordham-Skelton et al. 2002; Kerk et al. 2006). Anyway we do
need more facts to clarify the function network between phosphatases and other signals like
hormone, ion channels, kinases actions.
Finally, we can see that the biggest challenge for abiotic stress signal research is to elaborate
the network of kinases and phosphatases, and their relationship with a wide range of
substrates, as well as understand the phosphorylation states and how phosphorylation-
dependent activity culminates in the process of coping with a particular environmental
stress.
2.5. The role of TFs and genes in certain abiotic stress situations
By the end of signaling, the biggest assignment is to temporally and spatially regulate stress-
induced genes expression, and it is almost done at transcriptional level(Rushton and
Somssich 1998). Obviously the most contributing workers are transcription factors (TFs)
who modulate genes expression by binding to specific DNA sequences in the promoters of
target genes (Chaves and Oliveira 2004). Thanks to coordination between TFs and genes,
new transcripts are synthesized and stress adaptations have been realized within just a few
hours. Consequently, that is why TFs are such a group of powerful targets being so popular
in genetic engineering field aiming at improving stress resistance in crop plants. But, who
are they? While, most of them belong to several big families, naming AP2/ERF (ethylene
responsive element binding factor), Zn finger, basic leucine zipper (bZIP), basic helix-loop-
helix (bHLH), WRKY, MYB, and NAC. Indeed we frequently mentioned them in formal
description. So let's start to wander in their complicated regulatory network designed for
the also complex stress situations.
2.5.1. Drought
Based on recent data, the rate of land area experiencing drought is uprising and probably
goes up to 30% by the end of this century (Yi et al. 2010). And that is a big threaten for plants
lives, for drought is very likely to give rise to arrest of photosynthesis, disturbance of
metabolism and finally plant death (Jaleel et al. 2008). But plants will react efficiently. With a
few second of water loss, phosphorylation status of a protein will be triggered and later
when the suffering time reached hours or days long, gene expression and plant morphology
occur (Verslues and Bray, 2006). By researching on Arabidopsis plants under water-deficit
stress, more than 800 induced genes have been identified (Bray, 2004), who play key roles in
signal transduction, transcriptional regulation, cellular metabolism and transport, as well as
cellular structures protection. Meanwhile, when water deficit comes two major
