title: Interactions between soil fertility and climate drive variation in functional traits in New Zealand forests.

authors: Simpson, Angela Heather

subjects: plant functional trait

abstract: Plant functional traits provide a mechanistic approach to understanding the processes of environmental filtering and community assembly. Variation along environmental gradients results in changes in the adaptive values of traits. Climate and soil fertility are two dominant factors that drive these patterns of trait variation. These two factors simultaneously select for traits during environmental filtering. However, we do not understand how interactions between climate and soil fertility influence the variation in community-level traits of multiple plant organs. The roles of traits in New Zealand forests are also yet to be studied at a national scale.

This thesis aimed to determine the adaptive values of multiple functional traits across broad climate and soil fertility gradients in New Zealand forests. This was achieved by the following methods. Data were collected for leaf, stem, root, seed, flowering, and whole-plant traits from the 64 most common native trees in forests nationwide. Community composition and soil properties were measured at 324 plots across the country. For each plot, long-term average climate data were extracted from a model. A variable representing variation in soil fertility in the plots was derived by principal components analysis (PCA). Community-weighted mean (CWM) functional traits, i.e. average trait values weighted by the abundance of species, were calculated for each plot. Dimensionality of the specie-trait matrix was determined by PCA. Multiple linear regression was used to model the variation of each of the CWM traits as functions of mean annual temperature (MAT), vapour pressure deficit (VPD), soil fertility, soil fertility × MAT interaction, soil fertility × VPD interaction, total basal area and topography.

Five dimensions of trait variation were identified among New Zealand trees. Soil fertility was a more significant predictor of CWM traits than either of the climate variables. However, both of the interaction effects were significant for most traits and overrode the importance of the main effects. For example, in sites with high fertility soil, leaf economics traits varied from ‘slow’ in cool and dry conditions to ‘fast’ in warm and moist conditions, but in sites with low fertility, these traits were ‘slow’ in all climates. Therefore, the adaptive values of multiple functional traits of New Zealand forests varied depending on both soil fertility and climate.

This thesis provides the first recognition of the significant roles of the interaction effects between soil fertility and climate in driving variation in CWM traits from multiple plant organs. Climate and soil fertility interact in a way that influences CWM trait values independently from the influence of each environmental variable. These interactions are suspected to be important globally and should be tested for worldwide to confirm the generality of their effects. In conclusion, this thesis demonstrates that studying the relationships between CWM traits and soil fertility or climate independently is insufficient, when attempting to understand the process of environmental filtering. It is critical that the interaction effects between climate and soil fertility are included in future studies to enhance our understanding and ability to predict community-level responses to processes such as climate change.

text: Interactions between soil fertility and climate drive variation in functional traits in New Zealand forests. Plant functional traits provide a mechanistic approach to understanding the processes of environmental filtering and community assembly. Variation along environmental gradients results in changes in the adaptive values of traits. Climate and soil fertility are two dominant factors that drive these patterns of trait variation. These two factors simultaneously select for traits during environmental filtering. However, we do not understand how interactions between climate and soil fertility influence the variation in community-level traits of multiple plant organs. The roles of traits in New Zealand forests are also yet to be studied at a national scale.

This thesis aimed to determine the adaptive values of multiple functional traits across broad climate and soil fertility gradients in New Zealand forests. This was achieved by the following methods. Data were collected for leaf, stem, root, seed, flowering, and whole-plant traits from the 64 most common native trees in forests nationwide. Community composition and soil properties were measured at 324 plots across the country. For each plot, long-term average climate data were extracted from a model. A variable representing variation in soil fertility in the plots was derived by principal components analysis (PCA). Community-weighted mean (CWM) functional traits, i.e. average trait values weighted by the abundance of species, were calculated for each plot. Dimensionality of the specie-trait matrix was determined by PCA. Multiple linear regression was used to model the variation of each of the CWM traits as functions of mean annual temperature (MAT), vapour pressure deficit (VPD), soil fertility, soil fertility × MAT interaction, soil fertility × VPD interaction, total basal area and topography.

Five dimensions of trait variation were identified among New Zealand trees. Soil fertility was a more significant predictor of CWM traits than either of the climate variables. However, both of the interaction effects were significant for most traits and overrode the importance of the main effects. For example, in sites with high fertility soil, leaf economics traits varied from ‘slow’ in cool and dry conditions to ‘fast’ in warm and moist conditions, but in sites with low fertility, these traits were ‘slow’ in all climates. Therefore, the adaptive values of multiple functional traits of New Zealand forests varied depending on both soil fertility and climate.

This thesis provides the first recognition of the significant roles of the interaction effects between soil fertility and climate in driving variation in CWM traits from multiple plant organs. Climate and soil fertility interact in a way that influences CWM trait values independently from the influence of each environmental variable. These interactions are suspected to be important globally and should be tested for worldwide to confirm the generality of their effects. In conclusion, this thesis demonstrates that studying the relationships between CWM traits and soil fertility or climate independently is insufficient, when attempting to understand the process of environmental filtering. It is critical that the interaction effects between climate and soil fertility are included in future studies to enhance our understanding and ability to predict community-level responses to processes such as climate change.

year: 2015

title: The DNA Binding Protein Lsr2 from Mycobacterium tuberculosis

authors: Summers, Emma Louise

subjects: DNA binding protein

abstract: Lsr2 is a small, basic DNA binding protein that is highly conserved in mycobacteria and related actinomycetes. Lsr2 is essential for growth in Mycobacterium tuberculosis and previous studies have shown that Lsr2 is involved in down-regulating a wide range of genes involved in cell wall synthesis and metabolic functions. This regulatory function is likely to influence bacterial growth and survival.

This research investigated the biochemistry and 3D structure of Lsr2 from M. tuberculosis. Transmission electron microscopy (TEM) analysis of Lsr2 in complex with DNA revealed a regular fibril-like arrangement of protein coating double-stranded DNA. In addition, it was shown that Lsr2 physically protected DNA from DNase activity. The structure of the C-terminal DNA binding domain of Lsr2, determined by others part way through this research, prompted site directed mutagenesis of residues proposed to interact with DNA. Modification of arginine residues significantly reduced the binding of Lsr2 to DNA and fibril-like structures were not observed using TEM, for arginine mutants.

The first crystal structure of the N-terminal domain of Lsr2 is reported here. Two high resolution structures in monoclinic and hexagonal space groups were solved using X-ray crystallography and ab initio phasing. Proteolytic processing of the N-terminus of Lsr2 was revealed by the structure in P2₁ and this process was recreated using the protease trypsin which resulted in crystal formation in a P3₁21 space group. Both structures show linear chains of dimeric N-terminal Lsr2, as shown by crystallographic symmetry, linked by overlapping anti-parallel β-sheets, revealing a mechanism of protein oligomerisation. Oligomerisation only occurs after the removal of the first three residues M1, A2 and K3. In solution, protein oligomerisation was recreated with trypsin, resulting in the formation of large protein complexes. A change in DNA topology after the addition of trypsin to full-length Lsr2/DNA complexes was observed using TEM. This mechanism is likely to be important to M. tuberculosis under “stress” conditions where proteases are known to be upregulated and where cross-linking and condensation of DNA is critical.

text: The DNA Binding Protein Lsr2 from Mycobacterium tuberculosis Lsr2 is a small, basic DNA binding protein that is highly conserved in mycobacteria and related actinomycetes. Lsr2 is essential for growth in Mycobacterium tuberculosis and previous studies have shown that Lsr2 is involved in down-regulating a wide range of genes involved in cell wall synthesis and metabolic functions. This regulatory function is likely to influence bacterial growth and survival.

This research investigated the biochemistry and 3D structure of Lsr2 from M. tuberculosis. Transmission electron microscopy (TEM) analysis of Lsr2 in complex with DNA revealed a regular fibril-like arrangement of protein coating double-stranded DNA. In addition, it was shown that Lsr2 physically protected DNA from DNase activity. The structure of the C-terminal DNA binding domain of Lsr2, determined by others part way through this research, prompted site directed mutagenesis of residues proposed to interact with DNA. Modification of arginine residues significantly reduced the binding of Lsr2 to DNA and fibril-like structures were not observed using TEM, for arginine mutants.

The first crystal structure of the N-terminal domain of Lsr2 is reported here. Two high resolution structures in monoclinic and hexagonal space groups were solved using X-ray crystallography and ab initio phasing. Proteolytic processing of the N-terminus of Lsr2 was revealed by the structure in P2₁ and this process was recreated using the protease trypsin which resulted in crystal formation in a P3₁21 space group. Both structures show linear chains of dimeric N-terminal Lsr2, as shown by crystallographic symmetry, linked by overlapping anti-parallel β-sheets, revealing a mechanism of protein oligomerisation. Oligomerisation only occurs after the removal of the first three residues M1, A2 and K3. In solution, protein oligomerisation was recreated with trypsin, resulting in the formation of large protein complexes. A change in DNA topology after the addition of trypsin to full-length Lsr2/DNA complexes was observed using TEM. This mechanism is likely to be important to M. tuberculosis under “stress” conditions where proteases are known to be upregulated and where cross-linking and condensation of DNA is critical.

year: 2012

title: What works for midwives supporting māmā through emotional distress?

authors: Roia, Tiaan Mereana Manurangi

abstract: Pregnancy and the postnatal period are particularly vulnerable times for mothers’ mental health, with an increased risk of women experiencing depression and anxiety during this time. Therefore, understanding the level and type of service midwives provide to māmā who experience emotional distress is vital to know what midwives need in order to provide the right care to their clients.
The aim of this study was to find out what tools and resources community-based midwives find most helpful to support the needs of māmā. Seven semi-structured interviews were conducted, including four Māori midwives, who were able to provide insight on their experiences caring for mothers with mental health needs. Overall, the interviews reflected a strong sense of care and empathy from midwives during their time caring for mothers. Midwives appeared to rely on their interpersonal skills and intuition about emotional distress, and emphasised the importance of connecting with people and utilising support from their communities. Whilst midwives were interested and engaged with providing appropriate care to mothers, they were unbeknown to some of the clinical resources that could be available to their clients. The complexity of referrals and access to mental health services was central to the midwives’ frustration around caring for mothers, as well as a lack of education relating to kaupapa Māori, cultural competency, and mental health processes.
Recommendations based on this study are to provide midwives with education and training on topics like kaupapa Māori, on social and mental health resources and processes for referral to increase their ability to support and care for mothers who experience emotional distress. Improvements to the pathways for referrals and access to mental health services is essential. Future research should focus on understanding why midwives aren’t using a range of online apps and tools, and increase awareness of the available modes of support available.

text: What works for midwives supporting māmā through emotional distress? Pregnancy and the postnatal period are particularly vulnerable times for mothers’ mental health, with an increased risk of women experiencing depression and anxiety during this time. Therefore, understanding the level and type of service midwives provide to māmā who experience emotional distress is vital to know what midwives need in order to provide the right care to their clients.
The aim of this study was to find out what tools and resources community-based midwives find most helpful to support the needs of māmā. Seven semi-structured interviews were conducted, including four Māori midwives, who were able to provide insight on their experiences caring for mothers with mental health needs. Overall, the interviews reflected a strong sense of care and empathy from midwives during their time caring for mothers. Midwives appeared to rely on their interpersonal skills and intuition about emotional distress, and emphasised the importance of connecting with people and utilising support from their communities. Whilst midwives were interested and engaged with providing appropriate care to mothers, they were unbeknown to some of the clinical resources that could be available to their clients. The complexity of referrals and access to mental health services was central to the midwives’ frustration around caring for mothers, as well as a lack of education relating to kaupapa Māori, cultural competency, and mental health processes.
Recommendations based on this study are to provide midwives with education and training on topics like kaupapa Māori, on social and mental health resources and processes for referral to increase their ability to support and care for mothers who experience emotional distress. Improvements to the pathways for referrals and access to mental health services is essential. Future research should focus on understanding why midwives aren’t using a range of online apps and tools, and increase awareness of the available modes of support available.

year: 2023