The Plasma membrane Intrinsic Proteins (PIPs) in grey poplar Populus × canescens -identification of the PIP gene family and characterization of its function on multi-scale

Hochschulschrift

Zusammenfassung: This PhD thesis provides a molecular and physiological evaluation of the functionality of the PIP subfamily of aquaporins in leaf water relations and CO2 flux, of grey poplar (Populus x canescens) as a tree model system.Plasma membrane intrinsic proteins (PIPs) are widely studied in herbaceous plants; however, little is known regarding their role in water and CO2 transport in woody species. In the perennial woody plant Populus × canescens, 15 PIP genes were cloned and, according to the phylogenic analysis, all these genes had high homology with their Populus trichocarpa orthologs. The transcript abundance of the 15 PcPIP genes was examined in six different tissues of Populus × canescens, including young/mature/old leaves, roots, phloem and xylem. All PcPIP genes, except PIP2;8 and PIP2;10, were expressed in all above mentioned tissues. However, significant difference was present at the level of expression. To reveal the function of PIPs in poplar, transgenic poplar plants were generated in which the translation of PIP genes was down-regulated by RNA interference (RNAi). To target the two main groups of PIPs two specific RNAi cassettes for PIP1 and PIP2 genes were constructed. The on/off-target analysis revealed no additional targets of the two RNAi sequences besides PIP genes. With the PcPIP-RNAi transgenic plants, molecular screening was done on the transcript level by semi-quantitative RT-PCR and on the protein level by ELISA respectively. Based on these results, three PcPIP-RNAi transgenic lines were selected, in which PIP genes were the most down regulated.With the selected PcPIP-RNAi transgenic lines, a series of physiological and morphological studies were performed to characterize the plant’s response under optimal and multi-scale stress (elevated CO2, drought and heat stress) conditions. Under optimal conditions, the leaves of the PcPIP-RNAi transgenic lines had wider opened stomata and therefore had a higher net CO2 assimilation and transpiration rate compared with the wild type (WT) and empty vector control (EV) plants. As a consequence of the re-organization of the cellular structures, the leaves from PcPIP-RNAi transgenic plants had greater mesophyll conductance for CO2 (gm), higher leaf hydraulic conductance (Kleaf) and higher apoplastic water flux and overall, the leaves were smaller. Based on these results, it is concluded that PIP proteins not only play essential roles in whole leaf water and CO2 flux but also have important roles in the regulation of stomatal movement. Under multi-scale stress conditions, the PcPIP-RNAi transgenic lines displayed smaller total leaf area and above-ground biomass, lower chlorophyll content, lower water use efficiency (WUE) but higher pre-dawn leaf water potential. On the other hand, PIP can be a kind of CO2 transporter, which can affect plant carbon metabolism in the leaves. The PcPIP-RNAi transgenic lines had lower photorespiration rates and net CO2 assimilation rates, but higher internal CO2 concentration. The reduction in WUE of the PcPIP-RNAi transgenic lines could not be fully recovered after end of stresses. In addition, compared with WT/EV, PcPIP-RNAi transgenic lines showed higher isoprene emission under well-watered adaptation stage, but lower under severe drought and heat stress

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Albert-Ludwigs-Universität Freiburg, Dissertation, 2015

Klassifikation und Themen

• Klassifikation: Biowissenschaften, Biologie

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2016
• Urheber: Bi, Zhen
• Beteiligte Personen und Organisationen: Schnitzler, Jörg-Peter

Weitere Informationen

• DOI: 10.6094/UNIFR/10591
• URN: urn:nbn:de:bsz:25-freidok-105913
• Rechteinformation: Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 25.03.2025, 13:57 MEZ