The prevalence of food insecurity amongst refugees and asylum seekers during, and prior to, their early resettlement period in Australia: A cross-sectional analysis of the 'Building a New Life in Australia' data

With over 100 million humanitarian migrants globally, there is increasing pressure on high-income countries to offer resettlement opportunities. Humanitarian migrants face many challenges during pre-settlement and resettlement. One challenge is food insecurity (FI). The Building a New Life in Australia (BNLA) longitudinal cohort study gathered data from migrating units, that is, a group of humanitarian migrants included on the same visa application (n = 1599). Data were gathered in five annual waves (2013-2018). Data included food security status in four pre-settlement situations and during resettlement. The results of this secondary analysis of BNLA Wave One indicate that FI was highest in refugee camps (71%), followed by bridging visas (30%), community detention (17%), immigration detention (11%), and during early resettlement (9%). During early resettlement, respondents who were male, those from Afghanistan or Iran, and those living in a single person household reported the highest prevalence of FI. An association was found between having spent time on a bridging visa and FI during early resettlement (p < 0.01). This study's results are an important step in understanding the scale of FI and which sub-groups are most vulnerable, so the resources and policies of high-income countries can better meet food security needs during resettlement.

Clusters of 24-hour movement behavior and diet and their relationship with health indicators among youth: a systematic review

Movement-related behaviors (physical activity [PA], sedentary behavior [SB], and sleep) and diet interact with each other and play important roles in health indicators in youth. This systematic review aimed to investigate how PA, SB, sleep, and diet cluster in youth by biological sex; and to examine which cluster are associated with health indicators. This study was registered in PROSPERO (number: CRD42018094826). Five electronic databases were assessed. Eligibility criteria allowed studies that included youth (aged 19 years and younger), and only the four behaviors {PA, SB, sleep, and diet (ultra-processed foods [UPF]; fruits and vegetables [FV])} analyzed by applying data-based cluster procedures. From 12,719 articles screened; 23 were included. Of these, four investigated children, and ten identified clusters by biological sex. Sixty-six mixed cluster were identified including, 34 in mixed-sex samples, 10 in boys and 11 in girls. The most frequent clusters in mixed-sex samples were "High SB UPF Low Sleep", "Low PA High SB Satisfactory Sleep", and "High PA". The main difference in profiles according to sex was that girls' clusters were characterized by high sleep duration, whereas boys' clusters by high PA. There were a few associations found between cluster types and health indicators, highlighting that youth assigned to cluster types with low PA exhibited higher adiposity. In conclusion, the youth presented a range of clusters of behaviors, typically exhibiting at least one unhealthy behavior. Similar patterns were observed in both sexes with the biggest difference in time of sleep for girls and PA for boys. These findings underscore the importance of intervention strategies targeting multiple behaviors simultaneously to enhance health risk profiles and indicators in children and adolescents.

Associations between diet quality and dietary patterns and gestational diabetes mellitus in a low-risk cohort of pregnant women in Australia: a cross-sectional study

INTRODUCTION

Evidence of associations between the Mediterranean Diet Score (MDS) and Dietary Approaches to Stop Hypertension (DASH) score and gestational diabetes mellitus (GDM) in pregnant women is limited. This study examined changes in MDS and DASH and dietary patterns in Australian pregnant women between early and late pregnancy and their associations with GDM.

METHODS

The data from n = 284 participants were analysed. Diet quality indices and empirical dietary patterns were determined in early (15 ± 3 weeks gestation) and late pregnancy (35 ± 2 weeks gestation). Paired t-tests were used to examine changes in scores for diet quality indices and dietary patterns from early to late pregnancy. Logistic regression analysis was used to examine associations between GDM, diet quality indices and dietary patterns.

RESULTS

Three major dietary patterns were identified at early pregnancy. The first and second dietary patterns included unhealthier and healthier food groups, respectively, and the third comprised mixed food groups. Although diet quality scores did not change over time, consumption of the first dietary pattern increased (p = 0.01), and consumption of the second dietary pattern decreased by late pregnancy in women without GDM (p < 0.001).

CONCLUSION

No associations between DASH score, MDS and GDM were found; however an inverse association was observed between the first dietary pattern and GDM in late pregnancy (p = 0.023). Longitudinal studies are needed to examine diet quality and dietary patterns at early and late pregnancy to inform the development of tailored dietary advice for GDM.

Achieving high diet quality at eating occasions: findings from a nationally representative study of Australian adults

This study examined differences in food groups consumed at eating occasions by the level of adherence to dietary guidelines in Australian adults (≤19 years) and whether consumption differed with respect to age, sex and education levels. Secondary analysis of the 2011-2012 National Nutrition and Physical Activity Survey (n 9054) was performed, using one 24-h dietary recall with self-reported eating occasions. Dietary Guideline Index scores were used to assess adherence to the 2013 Australian Dietary Guidelines. Mean differences (95 % CI) in servings of the five food groups and discretionary foods at eating occasions were estimated for adults with higher and lower diet quality, stratified by sex, age group and education. Using survey-based t-tests, differences of at least half a serving with P values < 0·05 were considered meaningful. Compared with adults with lower diet quality, women and men aged 19-50 years with higher diet quality consumed more serves of vegetables at dinner (mean difference (95 % CI), women; 1·0; 95 % CI (0·7, 1·2); men: 0·9; 95 % CI (0·6, 1·3)) and fewer serves of discretionary foods at snacks (women: -0·7; 95 % CI (-0·9, -0·5); men: -1·0; 95 % CI (-1·4, -0·7). Other food groups, such as grains, dairy products and alternatives, meats and alternatives, were not significantly different between adults with lower and higher diet quality, across any eating occasions and age groups. Discretionary food intake at lunch, dinner and snacks was consistently greater among adults with lower diet quality, regardless of education level. Our findings identify dinner and snacks as opportunities to increase vegetable intake and reduce discretionary food intake, respectively.

Sociodemographic differences in dietary trends among Iranian adults: findings from the 2005-2016 Iran-WHO STEPS survey

OBJECTIVE

To examine trends in the intake of key food groups among Iranian adults between 2005 and 2016, overall, and according to sociodemographic characteristics.

DESIGN

Repeat cross-sectional data from the Iran-STEPwise approach to risk factor surveillance (Iran-WHO STEPS) 2005-2016 were analysed. Regression analyses were used to evaluate trends in the frequency of fruits, vegetables and fish intake and type of oil used over time. Interactions by sex, age and area of residence were examined.

SETTING

Iran.

PARTICIPANTS

225 221 Iranian adults.

RESULTS

The frequency of vegetables (β: -0·03; 95 % CI (-0·06, -0·00); P-trend = 0·030) and fish (β: -0·09; 95 % CI (-0·10, -0·08); P-trend < 0·001) intake and use of solid fat (OR: 0·70; 95 % CI (0·70, 0·72); P-trend < 0·001) declined, whilst the frequency of fruit intake (β-Coeff: 0·03, 95 % CI (0·01, 0·05); P-trend = 0·014) and liquid oil use (OR: 1·40; 95 % CI (1·3, 1·4); P-trend<0·001) rose. Rising trends in fruit intake were larger in mid-aged (40-60 years) and older (>60 years) adults (P-interaction < 0·001), whilst declines in vegetable (P-interaction < 0·001) and fish intake (P-interaction = 0·001) were larger in older adults. The declining use of solid fat was strongest in middle-aged and older adults (P-interaction = 0·035), while the increasing use of liquid oil was strongest in rural areas (P-interaction = 0·011).

CONCLUSIONS

During the nutrition transition, liquid oil use and the frequency of fruit intake rose, while the frequency of vegetables and fish intake declined. Nonetheless, the fatty acid composition and cooking methods are important considerations. The changes observed are concerning from a public health perspective and demonstrate the need for interventions and possible targets for tailored strategies.

Sedentary behaviour profiles and longitudinal associations with academic performance in youth: The UP&DOWN study

The current study evaluated longitudinal associations between profile transitions of context-specific sedentary behaviour (SB) and changes in academic performance (AP) among school-aged youth. Participants were 466 children and 717 adolescents (50.8% males) aged 8-18 years (children = 7.92 ± 0.41 years; adolescents = 11.85 ± 1.53 years). Non-school SBs and AP were evaluated at baseline and two years later. General linear mixed models were implemented, controlling for age, region, parental education, body mass index, and cardiorespiratory fitness. Cross-sectionally, participants with an Educative-profile (i.e., highest scores in doing homework with/without computer and reading for fun) had higher AP when compared to other profiles. Longitudinally, males who changed from a Screen- to an Educative-profile had higher AP than males who changed from an Educative- to a Social- or Screen-SB profile (p < 0.01). No significant differences were found in females. These findings show the importance of analysing SB patterns from a qualitative perspective (i.e., context-specific for boosting school children AP) and highlighting time spent in educative as the most positive for AP, as well the need to implement interventions to reduce time on screen and social behaviours, especially targeting males.

A longitudinal study of lifestyle behaviours in emerging adulthood and risk for symptoms of depression, anxiety, and stress

BACKGROUND

Little research has examined how lifestyle behaviours cluster together to contribute to mental health outcomes. The current study aimed to identify latent classes of emerging adult lifestyle behaviours (diet, physical activity, sedentary time, smoking, alcohol, cannabis, and other drug use) at age 20 years and their associations with depression, anxiety, and stress symptoms at age 22 and 27 years.

METHODS

Participants were 616 emerging adults enrolled in the Raine Study. Lifestyle classes at baseline were identified using latent class analysis. Longitudinal associations between latent class membership and risk of depression, anxiety, and stress symptoms were examined using logistic regression models.

RESULTS

Three lifestyle classes were identified: Class 1 (healthier pattern, n = 399 [64.8 %]), Class 2 (predominantly female, high substance-use, low physical activity pattern, n = 121 [19.6 %]), and Class 3 (predominantly male, high substance-use, poor diet pattern, n = 96 [15.6 %]). Following adjustment, Class 2 were at a higher risk of depression, anxiety, and stress symptoms at age 22 years, and a higher risk of anxiety and stress symptoms at age 27 years, compared to Class 1.

LIMITATIONS

This study was limited by reliance on self-report data, lack of available indicators for parental socioeconomic status, and some measurement inconsistencies across variables. Adherence to lifestyle clusters over time was not assessed.

CONCLUSIONS

Latent classes of lifestyle behaviours were identified among emerging adults, and differences in mental health outcomes were found among the classes at two prospective time points. Future research and prevention strategies for common mental disorders should target emerging adults and focus on lifestyle patterns.

Dietary patterns derived using principal component analysis and associations with sociodemographic characteristics and overweight and obesity: A cross-sectional analysis of Iranian adults

Introduction

This study examined the cross-sectional association between household dietary patterns and sociodemographic characteristics and BMI in a nationally representative sample of Iranian adults.

Methods

Data on 6,833 households (n = 17,824 adults) from the National Comprehensive Study on Household Food Consumption Pattern and Nutritional Status 2001-2003 were used. Principal component analysis (PCA) was used to extract dietary patterns from three household 24-h dietary recalls. Linear regression analyses were used to examine associations between dietary patterns and sociodemographic characteristics and BMI.

Results

Three dietary patterns were identified: the first was characterized by high citrus fruit intake, the second by high hydrogenated fats intake and the third by high non-leafy vegetables intake. The first and third patterns were associated with household heads with higher education and living in urban areas, while the second was associated with household heads with lower education and living in rural areas. All dietary patterns were positively associated with BMI. The strongest association was found with the first dietary pattern (β: 0.49, 95% CI: 0.43, 0.55).

Discussion

While all three dietary patterns were positively associated with BMI, the sociodemographic characteristics of Iranian adults who consumed them differed. These findings inform the design of population-level dietary interventions to address rising obesity rates in Iran.

Using compositional data analysis to explore accumulation of sedentary behavior, physical activity and youth health

PURPOSE

The study aimed to describe youth time-use compositions, focusing on time spent in shorter and longer bouts of sedentary behavior and physical activity (PA), and to examine associations of these time-use compositions with cardiometabolic biomarkers.

METHODS

Accelerometer and cardiometabolic biomarker data from 2 Australian studies involving youths 7-13 years old were pooled (complete cases with accelerometry and adiposity marker data, n = 782). A 9-component time-use composition was formed using compositional data analysis: time in shorter and longer bouts of sedentary behavior; time in shorter and longer bouts of light-, moderate-, or vigorous-intensity PA; and "other time" (i.e., non-wear/sleep). Shorter and longer bouts of sedentary time were defined as <5 min and ≥5 min, respectively. Shorter bouts of light-, moderate-, and vigorous-intensity PA were defined as <1 min; longer bouts were defined as ≥1 min. Regression models examined associations between overall time-use composition and cardiometabolic biomarkers. Then, associations were derived between ratios of longer activity patterns relative to shorter activity patterns, and of each intensity level relative to the other intensity levels and "other time", and cardiometabolic biomarkers.

RESULTS

Confounder-adjusted models showed that the overall time-use composition was associated with adiposity, blood pressure, lipids, and the summary score. Specifically, more time in longer bouts of light-intensity PA relative to shorter bouts of light-intensity PA was significantly associated with greater body mass index z-score (zBMI) (β = 1.79; SE = 0.68) and waist circumference (β = 18.35, SE = 4.78). When each activity intensity was considered relative to all higher intensities and "other time", more time in light- and vigorous-intensity PA, and less time in sedentary behavior and moderate-intensity PA, were associated with lower waist circumference.

CONCLUSION

Accumulating PA, particularly light-intensity PA, in frequent short bursts may be more beneficial for limiting adiposity compared to accumulating the same amount of PA at these intensities in longer bouts.

Associations between diet quality and obesity in a nationally representative sample of Iranian households: A cross-sectional study

OBJECTIVE

Research examining associations between diet quality and obesity in Iranian adults is limited by small and non-representative samples. This study examined associations between two diet quality indices and obesity risk in a nationally representative sample of Iranian adults and interactions by sex and area of residence.

METHODS

Data on 18,307 adults (mean age 37 [SD 15.2] years) were used from the Iranian National Survey 2001-2003. Two diet quality indices (Healthy Eating Index 2015, HEI-2015, and Diet Quality Index International, DQI-I) were calculated from household 24-h dietary recalls. Multi-level regression analyses were used to examine the association between household diet quality and individual-level obesity risk, with interaction terms for sex and area of residence.

RESULTS

Higher household HEI-2015 and DQI-I were associated with higher risk of obesity (HEI-2015: relative risk ratio: 1.04, 95% CI: 1.03, 1.05; DQI-I: relative risk ratio: 1.02, 95% CI: 1.01, 1.02), with stronger effect sizes in adults living in rural areas.

CONCLUSIONS

Higher diet quality (HEI-2015 and DQI-I) was associated with higher obesity risk, which was stronger in adults living in rural areas. Due to the complexity of examining these associations in a Middle Eastern country undergoing a nutrition transition, longitudinal research is needed to confirm these findings.

Conceptualizing and Measuring Appetite Self-Regulation Phenotypes and Trajectories in Childhood: A Review of Person-Centered Strategies

This review uses person-centered research and data analysis strategies to discuss the conceptualization and measurement of appetite self-regulation (ASR) phenotypes and trajectories in childhood (from infancy to about ages 6 or 7 years). Research that is person-centered provides strategies that increase the possibilities for investigating ASR phenotypes. We first examine the utility of examining underlying phenotypes using latent profile/class analysis drawing on cross-sectional data. The use of trajectory analysis to investigate developmental change is then discussed, with attention to phenotypes using trajectories of individual behaviors as well as phenotypes based on multi-trajectory modeling. Data analysis strategies and measurement approaches from recent examples of these person-centered approaches to the conceptualization and investigation of appetite self-regulation and its development in childhood are examined. Where relevant, examples from older children as well as developmental, clinical and educational psychology are drawn on to discuss when and how person-centered approaches can be used. We argue that there is scope to incorporate recent advances in biological and psychoneurological knowledge about appetite self-regulation as well as fundamental processes in the development of general self-regulation to enhance the examination of phenotypes and their trajectories across childhood (and beyond). The discussion and conclusion suggest directions for future research and highlight the potential of person-centered approaches to progress knowledge about the development of appetite self-regulation in childhood.

Characterizing children's eating patterns: does the choice of eating occasion definition matter?

BACKGROUND

Recommendations to define eating occasions (EO) currently exist for research in adults, but not for children or adolescents. We examined how varying EO definitions affect the characterization of eating patterns in children and adolescents.

METHODS

Cross-sectional dietary data collected using a 24-h recall data during the 2011-12 Australian National Nutrition and Physical Activity Survey (1364 boys and 1337 girls aged 2-18 years) were analyzed. Eight definitions were applied: participant-identified, time-of-day, and 6 neutral definitions (EO separated by 15- or 60-min and/or an additional energy criterion of 21 or 210 kJ). Frequency of and total energy intake from meals, snacks, and all EO were estimated. F tests stratified by gender and age-group, were used to assess differences between definitions. Agreement between definitions of meal and snack frequencies was assessed using intraclass correlation coefficients (ICC). Linear regression was used to estimate the proportion of variance in total energy intake (kJ) and BMI z-score predicted by each definition.

RESULTS

Mean frequencies of meals and snacks differed between the participant-identified and time-of-day definitions, in boys and girls and for all age groups (P < 0.01). Across the six neutral definitions, there were differences between mean frequencies of EO with the largest mean difference observed for children aged 2-3 y (boys: 2.3, girls: 2.5; P < 0.003). Between the participant-identified and time-of-day definitions, there was good agreement for frequencies of snacks (ICC for both genders: 0.93) but not meals (boys: 0.36; girls: 0.38). The 15-min time interval plus 210 kJ definition of an EO consistently predicted the most variance in total energy intake (R2 range = 8.1-34.8). Definitions that delineated meals and snacks better predicted variance in BMI z-score, when compared to the neutral definitions.

CONCLUSIONS

How eating patterns are characterized vary depending on the EO definitions employed, particularly in young children. Variance in total energy intake was best predicted by a variation of the neutral definition whereas definitions that delineated meals and snacks performed better in relation to predicting BMI variance. Further international research that compares EO definitions in children will help inform a standard approach.

What do Australian adults eat for breakfast? A latent variable mixture modelling approach for understanding combinations of foods at eating occasions

BACKGROUND

The patterning of food intake at eating occasions is a poorly understood, albeit important, step towards achieving a healthy dietary pattern. However, to capture the many permutations of food combinations at eating occasions, novel analytic approaches are required. We applied a latent variable mixture modelling (LVMM) approach to understand how foods are consumed in relation to each other at breakfast.

METHODS

Dietary intake at breakfast (n = 8145 occasions) was assessed via 24-h recall during the 2011-12 Australian National Nutrition and Physical Activity Survey (n = 3545 men and n = 4127 women, ⩾19 y). LVMM was used to determine breakfast food profiles based on 35 food group variables, reflecting compliance with Australian Dietary Guidelines. F and adjusted-chi2 tests assessed differences in timing of consumption and participant characteristics between the breakfast profiles. Regression models, adjusted for covariates, were used to examine associations between breakfast food profiles and objective adiposity measures (BMI and waist circumference).

RESULTS

Five distinct profiles were found. Three were similar for men and women. These were labelled: "Wholegrain cereals and milks" (men: 16%, women: 17%), "Protein-foods" (men and women: 11%) and "Mixed cereals and milks" (men: 33%, women: 37%). Two "Breads and spreads" profiles were also found that were differentiated by their accompanying beverages (men) or type of grain (women). Profiles were found to vary by timing of consumption, participant characteristics and adiposity indicators. For example, the "Protein-foods" profile occurred more frequently on weekends and after 9 am. Men with a "Bread and spreads (plus tea/coffee)" profile were older (P < 0.001) and had lower income and education levels (P < 0.05), when compared to the other profiles. Women with a "Protein-foods" profile were younger (P < 0.001) and less likely to be married (P < 0.01). Both men and women with a "Wholegrain cereals and milks" profile had the most favourable adiposity estimates (P < 0.05).

CONCLUSIONS

We identified five breakfast food profiles in adults that varied by timing of consumption, participant characteristics and adiposity indicators. LVMM was a useful approach for capturing the complexity of food combinations at breakfast. Future research could collect contextual information about eating occasions to understand the complex factors that influence food choices.

A comparison of diet quality indices in a nationally representative cross-sectional study of Iranian households

BACKGROUND

Iranian diet quality has been evaluated using indices that have not been created based on Iranian dietary guidelines. This study aimed to examine the applicability of two diet quality indices by examining their associations with nutrient adequacy, nutrient intakes and sociodemographics.

METHODS

Dietary data were collected using three 24-h dietary recalls from Iranian households. Nutrient adequacy was assessed using World Health Organization/Food and Agriculture Organization 2002 (WHO/FAO) cut points. Household diet quality was calculated using the Healthy Eating Index (HEI) and Diet Quality Index-International (DQI-I). Sociodemographics of the household members were assessed. Regression analyses were used to examine associations between diet quality and nutrient adequacy, and between sociodemographics and diet quality.

RESULTS

A total of 6935 households were included in the analysis. Higher household diet quality was associated with adequate intake of calcium (HEI: OR 1.11, 95% CI: 1.10, 1.13; DQI-I: OR 1.14, 95% CI: 1.13, 1.16), vitamin C (HEI: OR 1.19, 95% CI: 1.17, 1.20; DQI-I: OR 1.12, 95% CI: 1.11, 1.12) and protein (HEI: OR 1.01, 95% CI: 1.00, 1.02; DQI-I: OR 1.09, 95% CI: 1.08, 1.09). Higher household diet quality was associated with household heads who were older (> 56 years old) (HEI: β 2.06, 95% CI: 1.63, 2.50; DQI-I β 2.90, 95% CI: 2.34, 3.45), higher educated (college/university completed) (HEI: β 4.54, 95% CI: 4.02, 5.06; DQI-I: β 2.11, 95% CI: 1.45, 2.77) and living in urban areas (HEI: β 2.85, 95% CI: 2.54, 3.16; DQI-I: β 0.72, 95% CI: 0.32, 1.12).

CONCLUSIONS

Based on associations with nutrient adequacy and sociodemographics, the applicability of two diet quality indices for assessing the diet quality of Iranian households was demonstrated. Results also indicated DQI-I may be more applicable than HEI for evaluating Iranian nutrient adequacy. Findings have implications for the design and assessment of diet quality in Iranian populations. Future research should examine the link between these diet quality indices and health outcomes.

Eating occasion situational factors and sugar-sweetened beverage consumption in young adults

Background

Young adulthood represents an influential transitional period marked by poor dietary habits and excess weight gain. Sugar-sweetened beverages (SSB) are a major source of excess caloric intake among young adults, yet little is known about the correlates of SSB consumption. This study examines the individual and situational correlates of SSB consumption, using real-time assessment of Australian young adults’ eating occasions.

Methods

Dietary, sociodemographic and health behaviour data were collected during the Measuring EAting in Everyday Life (MEALS) study (n = 675 adults, 18–30 y). Participants reported all foods and beverages consumed over 3–4 non-consecutive days using a real-time Smartphone food diary application (“FoodNow”). For every eating occasion, food and beverage intake was recorded along with situational characteristics (eating location, purchase location, presence of others and activities while eating). A beverage occasion was defined as any eating occasion where a beverage was consumed and a SSB occasion was defined as any eating occasion where a SSB was consumed. Multilevel logistic regression was used to examine individual and situational characteristics with SSB intake at beverage occasions (i.e. factors associated with choosing a SSB over other non-alcoholic beverages) and to examine factors associated with consuming a SSB at any occasion where food and/or beverages were consumed.

Results

Thirty-five percent of participants consumed SSBs during the recording period (n = 237). Of the 2185 beverage eating occasions reported by SSB consumers, 481 (20%) contained a SSB. SSB were rarely consumed on their own (i.e. other foods were present). Having a lower than tertiary education (odds ratio [95% confidence interval]: 1.53 [1.16, 2.01]; p < 0.01); eating in a café/restaurant, compared to at home (3.02 [1.58, 5.78]; p < 0.001), and purchasing beverages from a convenience outlet, compared to a supermarket/grocery store (4.58 [2.85, 7.38]; p < 0.001) were associated with SSB intake at beverage eating occasions. Similar associations were also found when all food and/or beverage eating occasions were examined.

Conclusion

In this study, SSB were often consumed with other foods and intake was associated with individual and situational factors. Further studies are needed to confirm these findings and explore how SSB are consumed in relation to their accompanying foods.

Does modality matter? A latent profile and transition analysis of sedentary behaviours among school-aged youth: The UP&DOWN study

The aims of this study were to identify profiles of sedentary behaviour (SB) patterns, based on leisure-time self-reported SB modalities (screen, educative, social, and relaxing) and to evaluate changes in these profiles over 2 years among Spanish youth aged 8-18 years. Latent profile analysis (LPA), a data-driven analytic approach, was used to identify groups of boys and girls (n = 1553; 48% girls; mean±SD age: 12.56 ± 2.49 y) with distinct SB profiles using the SB modalities (time/d) as input variables. Latent transition analysis, an extension of LPA that uses longitudinal data, was used to analyse 2-year changes in these profiles. At baseline, four and three SB profiles were found among boys (labelled: screen, educative, social, and relaxing) and girls (labelled: screen/social, educative, and relaxing), respectively. Overall, more girls (range: 48%-67%) had the same profile over time, than boys (40%-52%). Participants with a screen or relaxing SB profile at baseline were more likely to have an educative profile after 2 years. Youth with a social and an educative SB profile at baseline were more likely to transition to profiles characterized by higher screen and social SB, respectively. Using a novel and person-centered approach, this study identified gender-specific SB profiles that were moderately stable over time.

Identification of health-related behavioural clusters and their association with demographic characteristics in Irish university students

Background

Students engage in risky health-related behaviours that influence their current and future health status. Health-related behaviours cluster among adults and differently based on sub-populations characteristics but research is lacking for university populations. Examining the clustering of health- related behaviours can inform our initiatives and strategies, while examining cluster members’ characteristics can help target those who can prosper most from health promotion efforts. This study examines the clustering of health-related behaviours in Irish university students, and investigates the relationship with students’ sex, age, field of study and accommodation type.

Methods

An online survey was completed by 5672 Irish university students (51.3% male; 21.60 ± 5.65 years) during 2014. Two-step cluster analysis was used to understand how health-related behaviours (physical activity, smoking, alcohol intake, drug use and dietary habits) cluster among male and female students. Binary logistic regressions were conducted to examine the likelihood of students falling into certain clusters based on their characteristics.

Results

Five cluster groups were identified in males and four in females. A quarter of males were categorised as ideal healthy with older students and those from certain fields of study having a higher likelihood of being classified in a low physical activity and poor diet (OR = 1.06–2.89), alcohol consumption (OR = 1.03–3.04), or smoking and drug use (OR = 1.06–2.73) cluster. Forty-five percent of females were categorised as ideal healthy with older females more likely to be in a low active and smoking cluster (OR = 1.03), and less likely to be in a convenience food cluster (OR = 0.96). Females from certain fields of study were also more likely to be classified in these clusters (OR = 1.59–1.76). Students living away from their family home had in increased likelihood of being in a cluster related to a higher frequency of alcohol consumption (OR = 1.72–3.05).

Conclusion

Health-related behaviours cluster among this population and need to be taken into account when designing multi-health interventions and policies. These findings can be used to target student groups at risk, leading to more efficient and successful health promotion efforts. The addition of modules providing information regarding health-related behaviours are advised in all fields of study.

Eating patterns of Australian adults: associations with blood pressure and hypertension prevalence

PURPOSE

Eating patterns have been linked to obesity, an established risk factor for hypertension; however, their contribution to hypertension is poorly understood. This study aimed to examine associations of frequency of meals, snacks and all eating occasions (EO), and temporal eating patterns, with blood pressure (BP) and hypertension.

METHODS

Dietary data collected via two 24-h recalls during the 2011-2012 Australian National Nutrition and Physical Activity Survey (n = 4482 adults, ≥ 19 years) were analysed. Frequencies of EO, meals, and snacks were calculated. Temporal eating patterns were determined using latent class analysis. Multivariate regression models assessed associations of eating patterns with systolic BP (SBP), diastolic BP (DBP), and hypertension prevalence.

RESULTS

Among men, a higher snack frequency was inversely associated with DBP [β = - 0.59, 95% confidence interval (CI) (- 1.12, - 0.07)] and hypertension [odds ratio (OR) 0.86, 95% CI (0.75, 0.98)] after adjustment for covariates and BMI. However, these associations disappeared after additional adjustment for total energy intake and overall diet quality. Among women, a temporal eating pattern characterized by a later "lunch" meal was associated with SBP [β = 2.45, 95% CI (0.05, 4.84)], DBP [β = 1.69, 95% CI (0.25, 3.13)], and hypertension [OR = 1.49, 95% CI (1.00, 2.22)], when compared to a "conventional" eating pattern.

CONCLUSIONS

In this study, an inverse association found between snack frequency and BP among men disappeared after adjustment for dietary factors and a "later lunch" pattern was associated with higher BP in women. Future research is needed to understand the relationship and potential mechanistic pathways between eating patterns and BP.

Patterning of neighbourhood food outlets and longitudinal associations with children's eating behaviours

This study examined cross-sectional and prospective associations between typologies of neighbourhood food environment and dietary patterns among 10-12 year-old children. Baseline data were collected in 2003 and follow-up data in 2006 from children in Melbourne or Geelong. Parents completed a food frequency questionnaire at both time points. 'Healthful' and 'energy-dense' dietary pattern scores were computed. A Geographic Information System was used to determine the presence or absence of food outlets (cafés/restaurant; fast food; supermarkets/grocery stores; convenience store; greengrocer; and butcher, seafood or poultry retailer) within an 800 m road network buffer of home. Three typologies were identified: 1-variety of food outlets, including those selling core/fresh foods (n = 96); 2-café/restaurant and convenience (n = 160); 3-few types of outlets (n = 208). Latent class analysis was used to identify underlying unobservable typologies of neighbourhood food outlet availability. Linear mixed models were fitted to determine cross-sectional (n = 439) and longitudinal (n = 173) associations between the three identified neighbourhood typologies and each (log-transformed) dietary pattern, accounting for clustering within families and schools. There was little evidence of cross-sectional associations. The longitudinal analyses showed that compared to those with a variety of food outlets, those with few types had 25% lower scores for the healthful dietary pattern (p < 0.05) three years later. For optimal dietary patterns, availability of a variety of food outlets close to home, particularly those where core/fresh foods are available, may be important.

Are dietary inequalities among Australian adults changing? a nationally representative analysis of dietary change according to socioeconomic position between 1995 and 2011-13

BACKGROUND

Increasing inequalities in rates of obesity and chronic disease may be partly fuelled by increasing dietary inequalities, however very few nationally representative analyses of socioeconomic trends in dietary inequalities exist. The release of the 2011-13 Australian National Nutrition and Physical Activity Survey data allows investigation of change in dietary intake according to socioeconomic position (SEP) in Australia using a large, nationally representative sample, compared to the previous national survey in 1995. This study examined change in dietary intakes of energy, macronutrients, fiber, fruits and vegetables among Australian adults between 1995 and 2011-13, according to SEP.

METHODS

Cross-sectional data were obtained from the 1995 National Nutrition Survey, and the 2011-13 National Nutrition and Physical Activity Survey. Dietary intake data were collected via a 24-h dietary recall (n = 17,484 adults) and a dietary questionnaire (n = 15,287 adults). SEP was assessed according to educational level, equivalized household income, and area-level disadvantage. Survey-weighted linear and logistic regression models, adjusted for age, sex/gender and smoking status, examined change in dietary intakes over time.

RESULTS

Dietary intakes remained poor across the SEP spectrum in both surveys, as evidenced by high consumption of saturated fat and total sugars, and low fiber, fruit and vegetable intakes. There was consistent evidence (i.e. according to ≥2 SEP measures) of more favorable changes in dietary intakes of carbohydrate, polyunsaturated and monounsaturated fat in higher, relative to lower SEP groups, particularly in women. Intakes of energy, total fat, saturated fat and fruit differed over time according to a single SEP measure (i.e. educational level, household income, or area-level disadvantage). There were no changes in intake of total sugars, protein, fiber or vegetables according to any SEP measures.

CONCLUSIONS

There were few changes in dietary intakes of energy, most macronutrients, fiber, fruits and vegetables in Australian adults between 1995 and 2011-13 according to SEP. For carbohydrate, polyunsaturated and monounsaturated fat, more favorable changes in intakes occurred in higher SEP groups. Despite the persistence of suboptimal dietary intakes, limited evidence of widening dietary inequalities is positive from a public health perspective.

TRIAL REGISTRATION

Clinical trials registration: ACTRN12617001045303 .

Temporal eating patterns: associations with nutrient intakes, diet quality, and measures of adiposity

Background: Some evidence suggests that higher energy intake (EI) later in the day is associated with poor diet quality and obesity. However, EI at one eating occasion (EO) is also dependent on EI at surrounding EOs. Studies that examine the distribution of EOs across the day are rare.Objective: The aim of this study was to examine associations between temporal eating patterns, nutrient intakes, diet quality, and measures of adiposity in a representative sample of Australian adults.Design: Dietary data from two 24-h recalls collected during the cross-sectional 2011-2012 Australian National Nutrition and Physical Activity Survey were analyzed (n = 4544 adults, aged ≥19 y). Temporal eating patterns, based on the distribution of EOs across the day, were determined by using latent class analysis. Diet quality estimated adherence to healthy eating recommendations and was assessed by using the 2013 Dietary Guidelines Index (DGI). Multivariate regression models assessed associations between temporal eating patterns, nutrient intakes, diet quality, and adiposity (body mass index, waist circumference, weight status, and central weight status). Models were adjusted for potential confounders and energy misreporting.Results: Three patterns, labeled "conventional," "later lunch," and "grazing," were identified. Compared with a "conventional" or "later lunch" pattern, men and women with a "grazing" pattern had lower DGI scores and higher intakes of discretionary (noncore) foods (P < 0.05). Among women, the "grazing" pattern was associated with overweight or obesity (OR: 1.57; 95% CI: 1.15, 2.13) and central overweight or obesity (OR: 1.73; 95% CI: 1.19, 2.50). These associations were attenuated after the exclusion of energy misreporters and adjustment for total EI.Conclusions: This study found that a "grazing" temporal eating pattern was modestly but significantly associated with poorer diet quality and adiposity among women, after adjustment for covariates and energy misreporting. Future research should consider the impact of energy misreporting on the relation between temporal eating patterns and adiposity. This secondary analysis was registered at anzctr.org.au as ACTRN12617001029381.

Novel Online or Mobile Methods to Assess Eating Patterns

Purpose of Review

Recent developments in technology-based dietary assessment allow real-time data collection of eating occasions, yet their application to assessing eating pattern constructs has not been evaluated. The purpose of this review was to examine existing electronic and mobile food diary methods in relation to their ability to assess eating patterns constructs (e.g. patterning, format and context of eating occasions).

Recent Findings

A systematic search of electronic databases identified 18 dietary assessment methods. Multiple methods with diverse technological capabilities have been developed, yet few studies report on their ability to assess all eating pattern constructs, particularly eating occasion context. Validity of the methods to assess overall dietary intake was found to be similar to traditional dietary assessment methods.

Summary

A diverse range of methods are available for examining the patterning and format/content, but not context, of eating occasions. Further consideration of eating pattern constructs is required when developing dietary assessment methods.

Temporal eating patterns: a latent class analysis approach

Background

There is some evidence that large energy intakes towards the end of the day are associated with adverse health outcomes, however, studies of temporal eating patterns across the day are rare. This study examines the temporal eating patterns of Australian adults using latent class analysis (LCA), as a novel approach.

Methods

Dietary data (n = 2402 men and n = 2840 women, ≥19 years) from two 24-h recalls collected during the 2011–12 Australian National Nutrition and Physical Activity Survey were analyzed. LCA was performed to identify distinct temporal eating patterns based on whether or not an eating occasion (EO) occurred within each hour of the day. F and adjusted-chi² tests assessed differences in sociodemographic and eating patterns (e.g., meal, snack and EO frequency) between latent classes.

Results

Three patterns, labelled “Conventional” (men: 43%, women: 41%), “Later lunch” (men: 34%, women: 34%) and “Grazing” (men: 23%, women: 25%) were identified. Men and women with a “Grazing” pattern were significantly younger (P < 0.001) and a higher proportion were from major cities (P < 0.01) and were not married (men only, P = 0.01), compared to the “Conventional” and “Later lunch” patterns. The “Grazing” pattern was also characterized by a higher EO frequency (P < 0.01) and snack frequency (P < 0.001) and consumption of a higher proportion of total energy intake from snacks but a lower proportion of total energy intake from meals (P < 0.001).

Conclusions

This study identified three distinct temporal eating patterns in adults that varied by age, EO frequency, snack frequency and energy intake pattern. LCA is a useful approach to capture differences in EO timing across the day. Future research should examine associations between temporal eating patterns and health.

Meal Frequency but Not Snack Frequency Is Associated with Micronutrient Intakes and Overall Diet Quality in Australian Men and Women

BACKGROUND

Skipping breakfast is associated with poorer diet quality among adults, but evidence of associations for other eating patterns [e.g., eating occasion (EO), meal, or snack frequency] is equivocal. An understanding of how eating patterns are associated with diet quality is needed to inform population-level dietary recommendations.

OBJECTIVE

We aimed in this cross-sectional study to determine the relation between frequency of meals, snacks, and all EOs with nutrient intakes and diet quality in a representative sample of Australian adults.

METHODS

Dietary data for 5242 adults aged ≥19 y collected via two 24-h recalls during the 2011-2012 National Nutrition and Physical Activity Survey were analyzed. EO, meal, and snack frequency was calculated. Adherence to recommendations for healthy eating was assessed with the use of the 2013 Dietary Guidelines Index (DGI) and its subcomponents. Linear regression, adjusted for covariates and energy misreporting, was used to examine associations between eating patterns, energy-adjusted nutrient intakes, and the DGI-2013.

RESULTS

The frequency of meals, but not of snacks, was positively associated with micronutrient intakes, overall diet quality [men: β = 5.6 (95% CI: 3.9, 7.3); women: β = 4.1 (95% CI: 2.2, 5.9); P < 0.001], and DGI-2013 component scores for cereals, lean meat and alternatives, and alcohol intake (P < 0.05). A higher frequency of all EOs, meals, and snacks was positively associated with DGI-2013 scores for food variety, fruits, and dairy foods (P < 0.05). Conversely, a higher snack frequency was associated with a lower compliance with guidelines for discretionary foods and added sugars among men (P < 0.05).

CONCLUSIONS

These findings suggest that meal frequency is an important determinant of nutrient intakes and diet quality in Australian adults. Inconsistent associations for snack frequency suggest that the quality of snack choices is variable. More research examining the dietary profiles of eating patterns and their relations with diet quality is needed to inform the development of meal-based guidelines and messages that encourage healthy eating.

Characterizing eating patterns: a comparison of eating occasion definitions

BACKGROUND

To date, many approaches have been used to define eating occasions (EOs). A standard definition for EOs is required to facilitate further research.

OBJECTIVE

In this study, we examined the influence of differing definitions of EOs on the characterization of eating patterns.

DESIGN

Cross-sectional dietary data from two 24-h recalls collected during the 2011-12 Australian National Nutrition and Physical Activity Survey (n = 5242 adults, aged ≥19 y) were analyzed. Eight definitions were applied: participant-identified, time-of-day, and 6 neutral definitions (individual EOs separated by different time intervals and/or an additional energy criterion of 210 kJ). Frequency of and total energy intake from meals, snacks, and all EOs were estimated, as appropriate. Differences were tested by using F tests, stratified by sex and age group. Agreement between different definitions of meal and snack frequencies was assessed by using intraclass correlation coefficients (ICCs). For each definition, linear regression was used to estimate the proportion of variance in total energy intake (kJ) and amount of food intake (g) predicted by frequency of EOs and meals and snacks.

RESULTS

Among both sexes and across all age groups, mean frequencies of meals differed between the participant-identified and time-of-day definitions (mean difference range = 0.1-0.3; P < 0.001). There were statistically significant differences between mean frequencies of EOs across the 6 neutral definitions (P < 0.001). There was good agreement for snacks (men: ICC = 0.89; women: ICC = 0.87) but not meal frequencies (men: ICC = 0.38; women: ICC = 0.36) between the participant-identified and time-of-day definitions. The neutral definition (15-min time interval plus energy criterion) best predicted variance in total energy intake (R(2) range = 19.3-27.8).

CONCLUSIONS

Different approaches to the definition of EOs affect how eating patterns are characterized, with the neutral definition best predicting variance in total energy intake. Further research that examines how different EO definitions affect associations with health outcomes is needed to develop consensus on a standard EO definition.

The clustering of diet, physical activity and sedentary behavior in children and adolescents: a review

Diet, physical activity (PA) and sedentary behavior are important, yet modifiable, determinants of obesity. Recent research into the clustering of these behaviors suggests that children and adolescents have multiple obesogenic risk factors. This paper reviews studies using empirical, data-driven methodologies, such as cluster analysis (CA) and latent class analysis (LCA), to identify clustering patterns of diet, PA and sedentary behavior among children or adolescents and their associations with socio-demographic indicators, and overweight and obesity. A literature search of electronic databases was undertaken to identify studies which have used data-driven methodologies to investigate the clustering of diet, PA and sedentary behavior among children and adolescents aged 5–18 years old. Eighteen studies (62% of potential studies) were identified that met the inclusion criteria, of which eight examined the clustering of PA and sedentary behavior and eight examined diet, PA and sedentary behavior. Studies were mostly cross-sectional and conducted in older children and adolescents (≥9 years). Findings from the review suggest that obesogenic cluster patterns are complex with a mixed PA/sedentary behavior cluster observed most frequently, but healthy and unhealthy patterning of all three behaviors was also reported. Cluster membership was found to differ according to age, gender and socio-economic status (SES). The tendency for older children/adolescents, particularly females, to comprise clusters defined by low PA was the most robust finding. Findings to support an association between obesogenic cluster patterns and overweight and obesity were inconclusive, with longitudinal research in this area limited. Diet, PA and sedentary behavior cluster together in complex ways that are not well understood. Further research, particularly in younger children, is needed to understand how cluster membership differs according to socio-demographic profile. Longitudinal research is also essential to establish how different cluster patterns track over time and their influence on the development of overweight and obesity.

Clustering of children's obesity-related behaviours: associations with sociodemographic indicators

BACKGROUND/OBJECTIVES

Research suggests obesity-related behaviours cluster together in children and adolescents, but how these cluster patterns differ by sociodemographic indicators remains unclear. Furthermore, few studies examining clustering of behaviours have included younger children or an objective measure of physical activity (PA) and sedentary behaviour. Therefore, the aim of this study was to examine clustering patterns of diet, PA and sedentary behaviour in 5- to 6- and 10- to 12-year-old children, and their cross-sectional associations with sociodemographic indicators.

SUBJECTS/METHODS

In this cross-sectional study, data from the baseline wave (2002/2003) of the Health Eating and Play study (HEAPS) were used. Questionnaires were completed by parents of Australian children aged 5-6 (n=362) and 10-12 years (n=610). Children wore accelerometers for up to 7 days. K-medians cluster analysis identified groups of children with similar diet, PA and sedentary behaviours. Chi-square tests assessed cluster differences by gender, maternal education and marital status.

RESULTS

For each age group, three reliable and meaningful clusters were identified and labelled 'most healthy', 'energy-dense (ED) consumers who watch TV' and 'high sedentary behaviour/low moderate-to-vigorous PA (MVPA)'. Clusters varied by sociodemographic indicators. For example, a higher proportion of older girls comprised the 'high sedentary behaviour/low MVPA' cluster (χ(2)=22.4, P<0.001). Among both age groups, the 'ED consumers who watch TV' cluster comprised more children with lower educated mothers (younger children: χ(2)=34.9, P<0.001; older children: χ(2)=27.3, P<0.001).

CONCLUSIONS

Identification of cluster patterns of obesity-related risk factors in children, and across sociodemographic groups may assist the targeting of public health initiatives, to those most in need.

Importance of sequences adjacent to the terminal tripeptide in the import of a peroxisomal Candida tropicalis protein in plant peroxisomes

The peroxisome targeting signal (PTS) required for import of the rat acyl-CoA oxidase (AOX; EC 1.3.3.6) and the Candida tropicalis multifunctional protein (MFP) in plant peroxisomes was assessed in transgenic Arabidopsis thaliana (L.) Heynh. The native rat AOX accumulated in peroxisomes in A. thaliana cotyledons and targeting was dependent on the presence of the C-terminal tripeptide S-K-L. In contrast, the native C. tropicalis MFP, containing the consensus PTS sequence A-K-I was not targeted to plant peroxisomes. Modification of the carboxy terminus to the S-K-L tripeptide also failed to deliver the MFP to peroxisomes while addition of the last 34 amino acids of the Brassica napus isocitrate lyase, containing the terminal tripeptide S-R-M, enabled import of the fusion protein into peroxisomes. These results underline the influence of the amino acids adjacent to the terminal tripeptide of the C. tropicalis MFP on peroxisomal targeting, even in the context of a protein having a consensus PTS sequence S-K-L.

Chloroplast acclimation in leaves of Guzmania monostachia in response to high light

Acclimation of leaves to high light (HL; 650 micromol m(-2) s(-1)) was investigated in the long-lived epiphytic bromeliad Guzmania monostachia and compared with plants maintained under low light (LL; 50 micromol m(-2) s(-1)). Despite a 60% decrease in total chlorophyll in HL-grown plants, the chlorophyll a/b ratio remained stable. Additionally, chloroplasts from HL-grown plants had a much lower thylakoid content and reduced granal stacking. Immunofluorescent labeling techniques were used to quantify the level of photosynthetic polypeptides. HL-grown plants had 30% to 40% of the content observed in LL-grown plants for the light-harvesting complex associated with photosystems I and II, the 33-kD photosystem II polypeptide, and Rubisco. These results were verified using conventional biochemical techniques, which revealed a comparable 60% decrease in Rubisco and total soluble protein. When expressed on a chlorophyll basis, the amount of protein and Rubisco was constant for HL- and LL-grown plants. Acclimation to HL involves a tightly coordinated adjustment of photosynthesis, indicating a highly regulated decrease in the number of photosynthetic units manifested at the level of the content of light-harvesting and electron transport components, the amount of Rubisco, and the induction of Crassulacean acid metabolism. This response occurs in mature leaves and may represent a strategy that is optimal for the resource-limited epiphytic niche.

The distinctive roles of five different ARC genes in the chloroplast division process in Arabidopsis

ARC (accumulation and replication of chloroplasts) genes control different aspects of the chloroplast division process in higher plants. In order to establish the hierarchy of the ARC genes in the chloroplast division process and to provide evidence for their specific roles, double mutants were constructed between arc11, arc6, arc5, arc3 and arc1 in all combinations and phenotypically analysed. arc11 is a new nuclear recessive mutant with 29 chloroplasts compared with 120 in wild type. All the phenotypes of the double mutants are unambiguous. ARC1 down-regulates proplastid division but is on a separate pathway from ARC3, ARC5, ARC6 and ARC11. ARC6 initiates both proplastid and chloroplast division. ARC3 controls the rate of chloroplast expansion and ARC11 the central positioning of the final division plane in chloroplast division. ARC5 facilitates separation of the two daughter chloroplasts. ARC5 maps to chromosome 3 and ARC11 and ARC6 map approximately 60 cM apart on chromosome 5.

Synthesis of medium-chain-length polyhydroxyalkanoates in arabidopsis thaliana using intermediates of peroxisomal fatty acid beta-oxidation

Polyhydroxyalkanoate (PHA) is a family of polymers composed primarily of R-3-hydroxyalkanoic acids. These polymers have properties of biodegradable thermoplastics and elastomers. Medium-chain-length PHAs (MCL-PHAs) are synthesized in bacteria by using intermediates of the beta-oxidation of alkanoic acids. To assess the feasibility of producing MCL-PHAs in plants, Arabidopsis thaliana was transformed with the PhaC1 synthase from Pseudomonas aeruginosa modified for peroxisome targeting by addition of the carboxyl 34 amino acids from the Brassica napus isocitrate lyase. Immunocytochemistry demonstrated that the modified PHA synthase was appropriately targeted to leaf-type peroxisomes in light-grown plants and glyoxysomes in dark-grown plants. Plants expressing the PHA synthase accumulated electron-lucent inclusions in the glyoxysomes and leaf-type peroxisomes, as well as in the vacuole. These inclusions were similar to bacterial PHA inclusions. Analysis of plant extracts by GC and mass spectrometry demonstrated the presence of MCL-PHA in transgenic plants to approximately 4 mg per g of dry weight. The plant PHA contained saturated and unsaturated 3-hydroxyalkanoic acids ranging from six to 16 carbons with 41% of the monomers being 3-hydroxyoctanoic acid and 3-hydroxyoctenoic acid. These results indicate that the beta-oxidation of plant fatty acids can generate a broad range of R-3-hydroxyacyl-CoA intermediates that can be used to synthesize MCL-PHAs.

Castor bean isocitrate lyase lacking the putative peroxisomal targeting signal 1 ARM is imported into plant peroxisomes both in vitro and in vivo

To understand and manipulate plant peroxisomal protein targeting, it is important to establish the universality or otherwise of targeting signals. Contradictory results have been published concerning the nature and location of the glyoxysomal/peroxisomal targeting signal of isocitrate lyase (ICL). L.J. Olsen, W.F. Ettinger, B. Damsz, K. Matsudaira, A. Webb, and J.J. Harada ([1993] Plant Cell 5: 941-952) concluded that the last 5 amino acids (AKSRM) of Brassica napus ICL were sufficient and the last 37 amino acids were necessary for targeting to Arabidopsis leaf peroxisomes. In contrast, R. Behari and A. Baker ([1993]) J Biol Chem 268: 7315-7322) could find no requirement for the almost identical carboxy-terminal sequence AKARM for import of Ricinus communis ICL into isolated sunflower cotyledon glyoxysomes. To resolve this discrepancy, the import characteristics of a mutant R. communis ICL lacking the last 19 amino acids of the carboxy terminus was studied. ICL delta 19 was able to be imported by isolated sunflower glyoxysomes and by tobacco leaf peroxisomes when expressed transgenically. These results demonstrate that the in vitro import system faithfully reflects targeting in vivo, and that the source of the organelles (Arabidopsis versus sunflower, leaf peroxisomes versus seed glyoxysomes) is not responsible for observed differences between B. napus and R. communis ICL. The R. communis enzyme would therefore appear to possess an additional glyoxysome/peroxisome targeting signal that is lacking in the B. napus protein.

Immunofluorescent quantitation of chloroplast proteins

Using scanning light microscopy software to detect and measure immunofluorescence in leaf sections Rubisco concentration in situ in chloroplasts has been accurately determined throughout development. The fluorescence measurements were calibrated by comparison with values for Rubisco accumulation obtained from rocket immuno-electrophoresis profiles of soluble protein from isolated cells and from chloroplasts using a purified sample of Rubisco as the standard. It has been shown that in situ immunofluorescence can be used for cytoquantitation of proteins within individual chloroplasts to a sensitivity of 1fg and also for the comparison of the protein levels in adjacent chloroplasts and cells. Several important applications of this new technique are discussed.

Characterization of chloroplast division using the Arabidopsis mutant arc5

arc5 is a chloroplast division mutant of Arabidopsis thaliana. To identify the role of ARC5 in the chloroplast replication process we have followed the changes in arc5 chloroplasts during their perturbed division. ARC5 does not affect proplastid division but functions at a later stage in chloroplast development. Chloroplasts in developing mesophyll cells of arc5 leaves do not increase in number and all of the chloroplasts in mature leaf cells show a central constriction. Young arc5 chloroplasts are capable of initiating the division process but fail to complete daughter-plastid separation. Wild-type plastids increase in number to a mean of 121 after completing the division process, but in the mutant arc5 the approximately 13 plastids per cell are still centrally constricted but much enlarged. As the arc5 chloroplasts expand and elongate without dividing, the internal thylakoid membrane structure becomes flexed into an undulating ribbon. We conclude that the ARC5 gene is necessary for the completion of the last stage of chloroplast division when the narrow isthmus breaks, causing the separation of the daughter plastids.

A putative Mg chelatase subunit from Arabidopsis thaliana cv C24. Sequence and transcript analysis of the gene, import of the protein into chloroplasts, and in situ localization of the transcript and protein

We have isolated and sequenced a cDNA from Arabidopsis thaliana cv C24 that encodes a putative Mg chelatase subunit. The deduced amino acid sequence shows a very high level of identity to a gene previously characterized from Antirrhinum majus (olive and also high similarity to bchH, a bacterial gene involved in the Mg chelatase reaction of bacteriochlorophyll biosynthesis. We suggest that this gene be called CHL H. Northern blot analyses were used to investigate the expression of CHL H, another putative Mg chelatase gene, ch-42, and ferrochelatase. The CHL H transcript was observed to undergo a dramatic diurnal variation, rising almost to its maximum level by the end of the dark period, then increasing slightly at the onset of the light and declining steadily to a minimum by the end of the light period; in contrast, transcripts for ch-42 and ferrochelatase remained constant. A model is proposed in which the CHL H protein plays a role in regulating the levels of chlorophyll during this cycle. In situ hybridization revealed that the transcripts are located over the surface of the chloroplasts, a feature in common with transcripts for the ch-42 gene. The CHL H protein was imported into the stromal compartment of the chloroplast and processed in an in vitro assay. Immunoblotting showed that the distribution of CHL H protein between the stroma and chloroplast membranes varies depending on the concentration of Mg+. In situ immunofluorescence was used to establish that the CHL H and CH-42 proteins are localized within the chloroplast in vivo.

arc6, an extreme chloroplast division mutant of Arabidopsis also alters proplastid proliferation and morphology in shoot and root apices

The arc6 (accumulation and replication of chloroplasts) mutant of Arabidopsis has only two greatly enlarged chloroplasts per mature leaf mesophyll cell compared with ninety chloroplasts per cell in the wild type. The mutation is a single nuclear gene and the plant phenotype is normal. Shoot and root apical meristems of arc6 plants have been examined to determine how early during plastid development the mutant arc6 phenotype can be recognised. In the cells of the arc6 apical meristem there are only two proplastids, which are larger than wild type with a highly variable morphology. In the cells of the leaf primordia where differentiation of proplastids to chloroplasts occurs arc6 plastids are larger and at a more advanced developmental stage than wild-type plastids. In arc6 root cells statoliths and other plastids also show grossly abnormal morphology and the statoliths are greatly increased in size. During arc6 stomatal guard cell development the perturbation in proplastid population dynamics affects plastid segregation and 30% of stomata lack plastids in one or both guard cells. Our evidence would suggest that ARC6 is expressed throughout the vegetative cells of the Arabidopsis seedling with major effects on both the proplastid phenotype and the proplastid population. ARC6 is the first gene to be identified in Arabidopsis which has a global effect on plastid development in cells arising from both the shoot and root meristems, and is of major importance in the nuclear control of plastid differentiation in higher plants.

Chloroplast Division and Expansion Is Radically Altered by Nuclear Mutations in Arabidopsis thaliana

We have isolated three mutants of Arabidopsis thaliana in which there is a sevenfold change in chloroplast number in fully expanded leaf mesophyll cells and increases and decreases in chloroplast number are compensated for by changes in chloroplast size. The changes are stably inherited in sexual crosses for three generations and mutant phenotypes are effected by changes at single recessive nuclear loci, termed arc loci. This is the first report of large, stably inherited changes in chloroplast number in higher plants, and represents a major advance toward the genetic dissection of the control of chloroplast division.

Rapid Image Analysis Screening Procedure for Identifying Chloroplast Number Mutants in Mesophyll Cells of Arabidopsis thaliana (L.) Heynh

To analyze the genetic control of the process of chloroplast division, a direct image analysis screening procedure has been developed in which mutants of Arabidopsis thaliana (L.) Heynh. var Landsberg erecta are selected on the basis of abnormal chloroplast number. The selection procedure is based on image analysis thresholding after iodine staining, which facilitates the automatic counting of chloroplasts in isolated mesophyll cells. M2 seedlings are screened for significant deviation from the wild type relationship between mesophyll cell size and chloroplast number. Mutants with both abnormally high and abnormally low chloroplast numbers were identified. Of 3500 individual M2 seedlings screened, 18 mutant lines have been isolated and shown to be stably inherited in three subsequent generations. The most extreme phenotypes show an 80% reduction or a 50% increase in chloroplast number per mesophyll cell.

Acetyl coenzyme A carboxylase in species of Triticum of different ploidy

The cellular amounts and cellular activities of acetyl CoA carboxylase (ACC; EC 6.4.1.2.) were determined in the first leaves of diploid, tetraploid and hexaploid species of Triticum (wheat). Per leaf the ACC activities were very similar in T. monococcum (2 χ), T. dicoccum (4 χ) and T. aestivum (6 χ). The ACC activity per chloroplast also showed little variation between species of different ploidy but since chloroplast number increases with ploidy, the ACC activities and ACC amounts per cell also increased with ploidy. These cellular increases in ACC amounts associated with increases in gene dosage were highly co-ordinated in the diploids T. monococcum and T. tauschii and their respective autotetraploids so the specific activity of ACC was highly conserved in these plants. The relevance of these findings to attempts to genetically manipulate lipid biosynthesis in chloroplasts is discussed.

Acetyl-CoA-carboxylase activity in normally developing wheat leaves

In order to investigate the role of acetyl CoA carboxylase (ACC) in the regulation of fatty-acid biosynthesis in chloroplasts, the activities and relative amounts of the enzyme have been measured in the tissue of wheat (Triticum aestivum L.) leaves undergoing development and cellular differentiation. The total activity in the first leaves of 5- to 7-d-old plants was similar but decreased to less than half in 9-d-old plants. The activity of ACC in the cells of the first leaf of 7-d-old plants doubled when cell age increased from 24 to 48 h, remained relatively constant for a further 24 h and then declined. The amount of ACC in cells increased 15-fold during the first 36 h of cell enlargement. Cells more than 36 h old contained about two-thirds the maximum amount of ACC found in younger cells. The most rapid phase of fatty-acyl accumulation in lipids was in cells aged between 60 and 84 h. Tenfold changes in the activity of ACC were observed when the assay conditions with respect to ATP, ADP, Mg(2+) and pH were changed to correspond to the physiological conditions in chloroplasts during light/dark transitions. This observation and the magnitude of the changes in the optimum activity and amount of ACC in leaf cells undergoing development are consistent with a role for ACC in the regulation of the flow of carbon from acetyl CoA to fatty acids in chloroplasts.

The control of chloroplast number in wheat mesophyll cells

Chloroplast number per cell and mesophyll cell plan area were determined in populations of separated cells from the primary leaves of different wheat species representing three levels of ploidy. Mean chloroplast number per cell increases with ploidy level as mean cell size increases. But in addition the analysis of individual cells clearly shows that cells of a similar size but from species of different ploidies have similar numbers of chloroplasts. We conclude that the number of chloroplasts within a cell is closely correlated (P<0.001) with the size of the cell and this relationship is consistent for species of different ploidies over a wide range of cell sizes. These results are discussed in relation to the hypothesis that chloroplast number in leaf mesophyll cells is determined by the size of the cell.

Variation in cellular ribulose-1,5-bisphosphate-carboxylase content in leaves of Triticum genotypes at three levels of ploidy

Ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 1.1.39) (RuBPCase) was quantified using polyacrylamide-gel electrophoresis in whole 9-d-old first leaves of 14 genotypes of Triticum, and cellular RuBPCase levels calculated. Diploids, tetraploids and hexaploids were analysed and it was confirmed that the RuBPCase level per cell is closely related to ploidy in wheat. Inter-genotypic variation in RuBPCase levels per cell and per leaf were surveyed. It was found that the interactions between leaf size, cell size and RuBPCase levels result in small variations in RuBPCase levels per unit leaf area between genotypes.

Some effects of 4-chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone (San 9785) on the development of chloroplast thylakoid membranes in Hordeum vulgare L

Chloroplast ultrastructural and photochemical features were examined in 6-d-old barley (Hordeum vulgare L. cv. Sundance) plants which had developed in the presence of 4-chloro-5-(dimethylamino)-2-phenyl-3(2H)-pyridazinone (San 9785). In spite of a substantial modification of the fatty-acid composition of thylakoid lipids there were no gross abnormalities in chloroplast morphology, and normal amounts of membrane and chlorophyll were present. Fluorescence kinetics at 77K demonstrated considerable energetic interaction of photosystem (PS)I and PSII chlorophylls within the altered lipid environment. An interference with electron transport was indicated from altered room-temperature fluorescence kinetics at 20°C. Subtle changes in the arrangements of chloroplast membranes were consistently evident and the overall effects of these changes was to increase the proportion of appressed to nonappressed membranes. This correlated with a lower chlorophyll a/b ratio, an increase in the amount of light-harvesting chlorophylls as determined by gel electrophoresis and fluorescence emission spectra, and an increase in excitation-energy transfer from PSII to PSI, as predicted from current ideas on the organisation of photosystems in appressed and non-appressed thylakoid membranes.