"Understanding plant drought tolerance based on genome analysis of a model plant, Arabidopsis thaliana"

Environmental degradation and climate change have become severe global problems because of the explosive population increases and industrialization in developing countries. How can we deal with these problems? One of the keys is plant biotechnology based on genomics and transgenic technology. This is becoming more and more important for molecular breeding of crops and trees that can tolerate droughts. For this technology, we need to understand plant responses to drought stress at the molecular level, since higher plants respond to drought stress through various molecular and cellular processes as well as physiological processes. This talk will describe recent research on the functions of stress-inducible genes, regulation of gene expression in response to drought stress, and identification of many drought-inducible genes and their functions in a model plant, Arabidopsis thaliana. Arabidopsis genome sequence was determined in 2000. Based on genome analysis, a lot of genes have been identified that are involved in drought stress responses and tolerance. Similar genes have been also found in rice and poplar. These genes are now used in molecular breeding of drought-tolerant crops and trees. Recently, we are trying to develop drought-resistant rice and wheat by using these stress-inducible genes in combination with their promoters by transgenic technology. Plant biotechnology based on genomics has great potential to solve major problems related to food and environment caused by desertification in global warming.

"Drought tolerance in maize, an important crop in agriculture"

Drought, high salinity or extreme temperatures are responsible for adverse effects on plant growth and seed production. More precisely, drought and salinity are the major causes of crop loss worldwide. Plants must adapt to these stress conditions in order to maintain growth and complete their life cycle. This is achieved by the activation of cascades of molecular networks that lead to physiological, morphological and metabolic modifications in order to re-establish homeostasis at cellular level. Our group made a significant contribution to the understanding of stress tolerance in plants, describing abscisic acid (ABA) and water stress-induced genes in maize. (Nature 334 (1988), 262-264.). Later on we expanded our research to include the identification of regulatory elements, transcription factors and signalling intermediates. These tools prompted successful transgenic approaches to increase plant tolerance to osmotic stress. Because of the complexity of the stress responses several genes will have to be expressed to achieve biotechnologically useful effects. In this context, we are developing drought tolerant plants by making transgenic plants with a single regulatory gene (such as a transcription factor) which in turn regulate the expression of downstream genes involved in the stress response. Understanding of stress adaptive mechanisms in plants can bring important information in the long term purpose of crop improvement. Our current interest is to obtain crop plants which are better adapted to adverse environmental conditions. This is a major goal in molecular breeding programmes for drought, cold and salt resistance.

"Drought tolerance of resurrection plants in dry land areas"

Limited water availability in some areas of the earth has resulted in evolution of mechanisms to live with restricted water supply. The majority of higher plants is unable to survive desiccation to an air-dried state; only seeds or pollen can withstand this condition. However, a small group of vascular angiosperm plants, termed resurrection plants, have evolved unique mechanisms of desiccation tolerance. Resurrection plants can tolerate severe water loss, and mostly adjust their water content with the relative humidity in the environment. The plants grow in ecological niches where rainfall occurs seasonal. Resurrection plants can remain in the desiccated state, comparable to dry seeds. When rainfall occurs, the plants take advantage of the conditions, they resurrect, grow and produce seeds before other species growing from seeds can do so. The best studied resurrection plant is Craterostigma plantagineum. The objective of our research is to understand how resurrection plants survive desiccation.
Research so far has shown that desiccation tolerance is a complex trait which requires the synthesis of proteins and sugars. At present, genes isolated from resurrection plants undergo functional analysis to prove the role of the gene products. We expect that the understanding of desiccation tolerance will provide novel biotechnological targets for improving growth of agricultural plants in environments with water limitations and seasonal rainfall.