A few facts about anti-drought in plants

In agricultural production, the process of drought that occurs during cultivation is likely to cause a serious decline in output. A good example is that in maize, 4-day water stress during flowering can reduce yield by 50% (Claisen and Shaw 1970).

The process of evapotranspiration in plants can occur through secreted cells or through cutin, the most effective water-resistant cutin plant known to date is Vanilla, a orchid with fruit for extraction. Vanilla export. The cuticle of Vanilla plants is much more resistant to dehydration than PVC and LCP food preservation films (liquid crystal polymer) - (Kerstient 1996, Riederer & Schreiber 2001).

In plants with many drought-resistant mechanisms already known, however, the most important concern is still the mechanism of ABA impact on stomata to minimize water loss.

The plant turn is capable of sensing the moisture content of the soil and carrying out reactions in the direction of the positive direction (Eapen 2005). However, the mechanism of this process is not well understood. According to Qin & Gevaart 1999, ABA molecules play a key role in the stress process and are synthesized by the 9-cis-epoxycarotenoid dioxygenase gene. When water stress occurs, the endogenous ABA hormone content increases, causing a closed gas signal (Blatt 2000) and the activation process takes only a few minutes (Asmann 2000). At the end of water stress, ABA levels return to normal, unlocking stomata.

It is because of ABA's key role in the drought tolerance process that it becomes the research target of genetic technology to create drought-resistant varieties.

Vanilla tree (Photo: zin.ru)

One of the steps to determine the genetic system that controls the biosynthesis and ABA's ability to interact is to screen for mutations, then use this information for other plants. The research model selected is Arabidopsis thaliana, a plant object that has been studied extensively in molecular terms and fully controllable mutations.

ABA in plant physiology is known as a phytohormone that inhibits seed germination and development, the term drought strategy by regulating endogenous ABA is therefore impossible.

On the other hand, because ABA molecules can change the level of gene expression (inhibition or enhancement), it can also increase the activity of other stress-regulating molecules, especially its activity. As shown in the guard cell, the mutant that enhances the ABA sensitivity is targeted as a necessity ^[2] .

Currently, many genes have been known to increase the susceptibility of hormonal plants (Finkenstein et al. 2002). Two of the genes that are particularly interested in ERA 1 and EBH 1, the dysfunctional mutations in these genes increase the response of epithelial cells to ABA (Cutler et al. 1996; Hugouvieux et al. 2001; Pei et al. 1998) For that reason, mutations in these sites significantly reduced wilting during stress treatment.

In the ERA 1 mutation, the appearance of exogenous ABA causes stomata to remain in the maximum closed state. Allen's (2002), Hugouviex (2002) studies on ERA 1-2 mutants showed that ABA increased the response of stomata by the interaction process leading to more sensitive transmembrane channels of Calcium.

Gene ERA 1 encoded for the Beta subunit of the farnesyltransferase enzyme AtFTB, in 1996 Cutler argued that the response of Arabidopsis to ABA must be through association with AtFTB (farnesylation). All farnesyltransferase enzymes in plants have 2 sub-components Anpha and Beta, which are 2 single gene subtypes. However, in addition to farnesyltransferase, plants also have a prenylation (prenylation) enzyme other than geranylgeranyltransferase (which plays an important role in the metabolism of Carotein - Ingo Potrykus 2004; in the development of apical growth - Running 2004). Type 1 Geranylgeranyltransferase is an enzyme heterodimer with an Alpha sub-structure similar to Farnesyltransferase, the other sub-section is completely different. For this reason, according to preliminary studies of drought tolerant plants based on Farnesyltransferase's Alpha subunit mutation, geranylgeranyltransferase inactivation is also involved, an enzyme directly related to morphological development. object.

However, when choosing inactivated target is sub-section Beta, the current result is mutant era1, although it has good drought tolerance, but it is deformed by some organs and grows poorer than normal trees in the condition of enough water (Donneta 2000; Yalovsky200; Ziegelhoffer 2000). The creation of drought-resistant plants by losing the function of the Beta sub-component is still a challenge.

A recent study by Yangwang and colleagues found that in many of the two sub-inactivation methods, although more sensitive to ABA, endogenous ABA content in tissues is always higher than normal. The study also showed that it was possible to replace a dysfunctional mutant by using antisense with the promoter rd29A (rough inducible) induced by the drought process. In this way, under normal conditions, GM plants have no different yield than the original plants .

Refer:
^[1] Yang Wang, jifeng Ying, Monika Kuzma. (2005) Molecular tailoring of farnesylation for plant drought tolerance and yield protection. Tập tin Plant. 43, 413-424
^[2] Madhara Rao, AS Raghavendra, Janardhan Reddy. (2006) Physiology and Molecular Biology of Stress Tolerance in Plant. Springer. Chapter 1-2. Introduction, Water stress.

Nguyen Huu Hoang