Cell Wall Stress Response Research Articles

The yeasts Rho1p and Pkc1p regulate the transport of chitin synthase III (Chs3p) from internal stores to the plasma membrane.

During cell stress, Saccharomyces cerevisiae increases the synthesis of chitin and glucans to strengthen and repair the cell wall. In this study, we show that under conditions of cell stress, the steady-state localization of chitin synthase III (Chs3p) shifts from internal stores (chitosomes) to the plasma membrane (PM). This redistribution occurs rapidly and requires the activators of the cell wall stress response signaling pathway, the G protein Rho1p, and the protein kinase Pkc1p, but not the cell integrity response mitogen-activated protein kinase cascade. Furthermore, expression of activated forms of Rho1p or Pkc1p, in the absence of cell stress, is sufficient to redistribute Chs3p to the PM. In cells deficient for both the clathrin adaptor complex 1 and Chs6p, where Chs3p is transported to the PM by an alternative bypass pathway, cell wall stress did not cause mobilization of Chs3p, suggesting that Rho1p/Pkc1p regulate Chs3p exit from the trans-Golgi network. The mobilization of an intracellular reservoir of Chs3p presents a novel opportunity to investigate the genetic basis of regulated vesicular traffic.

Isolation of cDNAs differentially expressed in response to drought stress and characterization of the Ca-LEAL1 gene encoding a new family of atypical LEA-like protein homologue in hot pepper ( Capsicum annuum L. cv. Pukang)

Among various abiotic stresses, water deficit is one of the most severe environmental factors responsible for the reduction of crop yield in many parts of the world. By means of the mRNA differential display technique, seven cDNAs (pCa-DIs for Capsicum annuum drought induced) have been isolated that are rapidly induced when hot pepper plants are subjected to water stress (5–20% loss of fresh weight). For all of the isolated Ca-DIs, database search provided significant sequence similarity to previously described genes from different plant species. The predicted proteins encoded by the Ca-DI genes are putatively involved in processes as diverse as primary metabolism, protein degradation, cell wall modification and stress response, suggesting the complexity of cellular responses to drought stress in hot pepper plants. Particularly, we analyzed the detailed structural property and expression pattern of the Ca-DI4 ( Ca-LEAL1) gene. Sequence homology studies indicate that Ca-LEAL1 ( M r=19.3 kDa) belongs to a new family of atypical hydrophobic late embryogenesis-abundant-like (LEA-like) proteins. Expression analysis showed that Ca-LEAL1 was strongly activated by drought and salt stresses, and also in response to mechanical wounding in both local and systemic leaves. Moreover, the level of Ca-LEAL1 transcript was rapidly enhanced by exogenous application of ABA and ethylene. These results are consistent with the notion that an atypical hydrophobic Ca-LEAL1 protein is subject to control by diverse environmental factors and that ethylene, in conjunction with ABA, plays an important role in the regulation of the stress gene in hot pepper plants. The possible physiological functions of Ca-LEAL1 as well as other Ca-DI proteins in the adaptive process against drought stress are discussed

Sugarcane ESTs differentially expressed in immature and maturing internodal tissue

Two subtracted cDNA libraries were constructed by reciprocal subtractive hybridisation between sugarcane immature (low sucrose-accumulating) and maturing (high sucrose-accumulating) internodal tissue. The subtracted libraries contained high, moderate and low abundance transcripts. To isolate cDNAs differentially expressed during culm maturation, 400 random clones (200 from each library) were systematically arrayed onto nylon filters and screened with total cDNA probes prepared from immature and maturing culm poly (A) + RNA. Results indicated that 36 and 30% of the total number of cDNAs analysed were preferentially expressed in the immature and maturing culm, respectively. Northern analysis of selected clones confirmed culm developmental stage-specific and -preferential expression for most of the clones tested. Expressed Sequence Tags (ESTs) generated by partial sequence analysis for all 132 differentially expressed clones indicated 95 unique transcripts. Partial sequence information could assign putative identities to 66% of the differentially expressed ESTs. The majority of ESTs with a putative identity were homologous to genes associated with cell wall metabolism, carbohydrate metabolism, stress responses and regulation, where the specific ESTs identified in the immature and maturing culm were distinct from each other. No developmentally regulated ESTs directly associated with sucrose metabolism were detected. This suggests that growth and maturation of the sugarcane culm is associated with the expression of genes for a variety of processes. This study demonstrates that a combination of cDNA subtraction with macroarray screening is an effective strategy to identify and analyse candidate developmentally regulated genes in sugarcane.