Małgorzata Adamiec

The irradiance dependent transcriptional regulation of AtCLPB3 expression.

Transcript abundance analysis was applied to determine whether expression of genes coding for 50 principal constituents of chloroplast and mitochondria proteolytic machinery, i.e. isoforms of proteases and regulatory subunits of Clp and FtsH families as well as Deg group of chymotrypsin family are differentially expressed in response to acclimation to elevated irradiance. Of 50 genes analysed only a single one coding for ClpB3 regulatory subunit was found to be up-regulated and gene coding for Deg2 to be down-regulated significantly during acclimation to excessive irradiance conditions. Hierarchical clustering of transcript abundance data revealed that CLPB3 co-expressed tightly with genes coding for PAP1, GBF6 and bHLH family member transcription factors during the acclimation. It was found that CLPB3 contains cis-regulatory elements able to bind all three transcription factors. By performing analyses of publicly available transcriptomic data sets from a range of long-term abiotic stresses we suggest that PAP1 may mediate condition-dependent transcriptional response of CLPB3, induced by a group of long-term abiotic stresses.

Arabidopsis thaliana intramembrane proteases

Proteolysis is considered as a crucial factor determining the proper development of the plant and its efficient functioning in variable environmental conditions. The role of proteases in protein quality control and protein turnover processes is well documented. The results of studies performed in recent years reveal; however, that proteolytic enzymes also participate in signal transduction pathways by releasing membrane-anchored transcription factors in the process known as regulated intramembrane proteolysis (RIP). The first described intramembrane protease was identified in human cells in 1997. In turn, the first plant intramembrane protease was identified in 2005, in Arabidopsis thaliana. To date, most studies concerning the RIP process in plants have been performed on this model plant. The knowledge concerning the potential physiological role of RIP is very limited. However, continuously accumulating information concerning this issue indicates that RIP, like the other proteolytic mechanisms, has a significant effect on plant ontogenesis, acclimatization and fertility. The aim of this article is to gather and systemize the present knowledge concerning the intramembrane proteases in A. thaliana.

Teaching about Water Relations in Plant Cells: An Uneasy Struggle

University students often struggle to understand the role of water in plant cells. This study attempted to identify student difficulties (including misconceptions) concerning osmosis and plasmolysis and examined to what extent the difficulties could be ameliorated during a plant physiology course.

Arabidopsis thaliana egy2 mutants display altered expression level of genes encoding crucial photosystem II proteins

EGY2 is a zinc-containing, intramembrane protease located in the thylakoid membrane. It is considered to be involved in the regulated intramembrane proteolysis - a mechanism leading to activation of membrane-anchored transcription factors through proteolytic cleavage, which causes them to be released from the membrane. The physiological functions of EGY2 in chloroplasts remains poorly understood. To answer the question of what the significance is of EGY2 in chloroplast functioning, two T-DNA insertion lines devoid of EGY2 protein were obtained and the mutant phenotype and photosystem II parameters were analyzed. Chlorophyll fluorescence measurements revealed that the lack of EGY2 protease caused changes in non-photochemical quenching (NPQ) and minimum fluorescence yield (F0) as well as a higher sensitivity of photosystem II (PSII) to photoinhibition. Further immunoblot analysis revealed significant changes in the accumulation levels of the three chloroplast-encoded PSII core apoproteins: PsbA (D1) and PsbD (D2) forming the PSII reaction center and PsbC - a protein component of CP43, a part of the inner PSII antenna. The accumulation levels of nuclear-encoded proteins,Lhcb1-3, components of the major light-harvesting complex II (LHCII) as well as proteins forming minor peripheral antennae complexes, namely Lhcb4 (CP29), Lhcb5 (CP26), and Lhcb6 (CP24) remain, however, unchanged. The lack of EGY2 led to a significant increase in the level of PsbA (D1) with a simultaneous decrease in the accumulation levels of PsbC (CP43) and PsbD (D2). To test the hypothesis that the observed changes in the abundance of chloroplast-encoded proteins are a consequence of changes in gene expression levels, real-time PCR was performed. The results obtained show that egy2 mutants display an increased expression of PSBA and a reduction in the PSBD and PSBC genes. Simultaneously pTAC10, pTAC16 and FLN1 proteins were found to accumulate in thylakoid membranes of analyzed mutant lines. These proteins interact with the core complex of plastid-encoded RNA polymerase and may be involved in the regulation of chloroplast gene expression.

Are We Aware of What Is Going on in a Student’s Mind? Understanding Wrong Answers about Plant Tropisms and Connection between Student’s Conceptions and Metacognition in Teacher and Learner Minds

Problems with understanding concepts and mechanisms connected to plant movements have been diagnosed among biology students. Alternative conceptions in understanding these phenomena are marginally studied. The diagnosis was based on a sample survey of university students and their lecturers, which was quantitatively and qualitatively exploratory in nature (via a questionnaire). The research was performed in two stages, before and after the lectures and laboratory on plant movements. We diagnosed eight alternative conceptions before the academic training started. After the classes, most were not been verified, and in addition, 12 new conceptions were diagnosed. Additionally, we report that teachers are not aware of students’ possible misunderstandings. They do not perceive students’ troubles with switching between levels of representations, nor their alternative conceptions. A case of “curse of knowledge” was observed and academic teacher training is recommended. Additionally, the need for metacognition as a crucial element in laboratory activities seems supported by our presented results. Such metacognition refers to students as well as teachers, which leads to the conclusion that teachers should be aware of students’ way of thinking and the development of knowledge in one’s own mind.

New insight into plant intramembrane proteases

The process of proteolysis is a factor involved in control of the proper development of the plant and its responses to a changeable environment. Recent research has shown that proteases are not only engaged in quality control and protein turnover processes but also participate in the process which is known as regulated membrane proteolysis (RIP). Four families of integral membrane proteases, belonging to three different classes, have been identified: serine intramembrane proteases known as rhomboid proteases, site-2 proteases belonging to zinc metalloproteases, and two families of aspartic proteases: presenilins and signal peptide peptidases. The studies concerning intramembrane proteases in higher plants are, however, focused on Arabidopsis thaliana. The aim of the study was to identify and retrieve protein sequences of intramembrane protease homologs from other higher plant species and perform a detailed analysis of their primary sequences as well as their phylogenetic relations. This approach allows us to indicate several previously undescribed issues which may provide important directions for further research.

Erratum to: Arabidopsis thaliana intramembrane proteases

Studies performed on spp heterozygotes indicate that the protein is involved in pollen development and germination (Han et al. 2009). The SPPL1, SPPL2 and SPPL3 transcripts were detected in the tissues, roots, rosette leaves, cauline leaves, stems, flower-bud clusters, siliques and dry seeds (Tamura et al. 2008). The significant accumulation of all three transcripts was, however, observed during seed germination.