As sessile organisms, plants are subjected to environmental stress over their whole life. Soil salinity is a major environmental problem that leads to crop yield reduction. Salinity stress often causes serious damage and plants have developed a variety of suitable and efficient mechanisms to tolerate the environmental stress to adapt to adverse conditions. Responses of plants to stress rely on rapid and coordinate changes of gene expression and cellular, physiological and chemical processes. The expression of many genes and the level of endogenous plant hormones such as abscisic acid (ABA) and indole-3-acetic acid (IAA) are affected by abiotic stress, especially salinity and drought [1] and [2]. For example, under drought conditions, the increase of ABA level could trigger closure of stomata and regulate expression of many ABA-dependent stress-responsive genes [3]. Meanwhile, many genes are activated, leading to accumulation of some functional proteins involved in tolerating abiotic stress and/or protecting plants from oxidation damage [4] and [5]. In addition, during the response and adaptation to abiotic stress, many biochemical and physiological changes occur including accumulation of osmolytes such as soluble sugar and proline to facilitate osmo-regulation and to prevent oxidative damage due to disruption of reactive oxygen species (ROS) homeostasis [6], [7] and [8].
Recent data indicate that some key transcription factors involved in stress signals and hormonal signaling pathways act as regulators to control plant development under adverse growth conditions [9]. Molecular interaction and crosstalk between GA (gibberellins) and ABA have emerged as the key regulatory mechanisms of plant growth and development in response to environmental adversity. It is shown that DELLA proteins, that repress GA-activated gene expression and plant growth, function as regulatory hubs to integrate the GA-dependent development into environmental adaptation [10] and [11]. Salt stress usually leads to accumulation of DELLA and GA level decrease and slows plant growth and reduces biomass [1]. In addition, DELLA proteins are also able to promote the expression of genes encoding reactive oxygen species (ROS)-detoxifying enzymes to reduce ROS levels in cells after biotic or abiotic attack, thereby delaying cell death and enhancing tolerance [12]. In Arabidopsis, DELLA proteins have been shown to have a regulatory function in connecting and balancing cross-talks of antagonizing GA and ABA signaling [13] and [14].