Gene expression of halophyte Kosteletzkya virginica seedlings under salt stress at early stage.

Gene differential expression of Kosteletzkya virginica seedlings under salt stress at two time points (2, 24 h) in roots and leaves was analyzed using the cDNA-amplified fragment length polymorphism (cDNA-AFLP) technique. Polymorphic transcript-derived fragments (TDFs) among control plants and salt-treated plants were grouped into four main differential expression patterns: repression (A), de novo induction (B), up-regulation (C) and down-regulation (D). Among them, 34 differentially expressed gene fragments were homologous to known genes from other species and 4 were sequences with unknown functions. These differentially expressed genes can be classified into four groups according to their putative functions: (1) genes for re-establishing ion homeostasis and protecting the plant from stress damage; (2) genes involved in metabolism or energy and resuming plant growth and development under salt stress; (3) genes involved in regulation of gene expression; (4) genes for signal transduction. Changes of eight differentially expressed genes were confirmed by quantitative real time RT-PCR.

[Analysis of gene expression involved in the response to salt stress in the dicot halophyte Kosteletzkya virginica L. seedlings].

Kosteletzkya virginica L. Presl. is an obligate wetland species indigenous to southeastern US. Its niche in salt marsh foretells its high salinity tolerance. cDNA-AFLP technique was used to identify the gene transcriptional profiles of leaves and roots from K. virginica seedlings under salt stress in order to clarify the molecular architecture of stress tolerance in the dicot halophyte. Expression analysis over time intervals and under various salt stresses in leaves or roots showed that the quantitatively expressed pattern (in which genes were quantitatively up- or down-regulated under salt stress or fluctuate with different NaCl concentrations) was more prevalent than the qualitatively expressed pattern (in which genes were induced or silenced under salt stress) in K. virginica seedlings under salt stress. The qualitative pattern was appreciably more predominant than the quantitative one only in roots when exposed to salt stress for 2 h. Although each expression pattern was observed in leaves as well as in roots, the percentage of genes (i.e., up-/down-regulated or induced/silenced under salt stress) was dynamically changeable under salt stress at different time intervals. All these results indicated that there was no established formula of gene expression patterns in deciphering the sophisticated mechanism of plant salinity tolerance, considering that plants undergo a series of dynamically physiological and metabolic pathways in sensing and response to salt stress for different tissues and during different stages of stress. A number of Trivially distributed file system (TDFs) up-regulated or induced under salt stress from leaves and roots were sequenced, and the sequences were blasted against the NCBI non-redundant protein database using translated nucleotide query (Blastx). The TDFs from K. virginica seedlings involved in sensing and response to salt stress can be classified at least into three groups according to their putative functions: (1) genes for re-establishing ionic homeostasis or preventing from damage (specially genes for transporter); (2) genes for resuming plant growth and development under salt stress, such as key enzymes involved in energy synthesis or hormone regulatory pathway; (3) genes for signal transduction and so on. The relationship of expression patterns of these TDFs with the molecular mechanism of salt tolerance in K. virginica was discussed.

Relationship between differential gene expression patterns in functional leaves of maize inbreds & hybrids at spikelet differentiation stage and heterosis.

To understand the molecular mechanism of maize heterosis, differential gene expression patterns in functional leaves between 10 maize inbreds and 38 hybrids at spikelet differentiation stage were analyzed by using cDNA-AFLP. The correlation analysis of various differential gene expression patterns with the performance and heterosis of main maize agronomic traits was carried out. The main results are as follows: (1) There are differential gene expression patterns in quality and quantity between hybrids and their parents. The differential expression patterns in quality include: bands expressed only in one parent, bands expressed only in both parents, bands expressed only in one parent and F1, bands expressed only in F1. (2) At spikelet differentiation stage, there are large variations among different hybrids for the same differentially expressed patterns. In general from mean data, there were 25.22% bands expressed only in F1, 21.46% bands expressed in one parent and F1, 8.27% bands expressed only in both parents and 33.49% bands expressed only in one parent. (3) For bands expressed only in one parent, significant positive correlation was detected with the relationship to the performance of plant height. For bands expressed only in both parents, significant negative correlation was detected with the relationship to the heterosis of ear diameter. For bands expressed only in one parent and F1, significant negative correlations were detected with the relationships to the heterosis of rows per ear and seed weight per ear. However, for bands expressed only in F1, and for bands only in two parents or only in F1, no significant correlation was detected with the relationship to the performance and heterosis of all agronomic traits.