Is there a relationship between low-grade systemic inflammation and cognition in healthy people aged 60-75 years?

Although inflammation has been associated with cognitive impairment in dementia, less is known about its role in the cognition of middle to older aged healthy people. This study utilised baseline data from the Australian Research Council Longevity Intervention (ARCLI) trial to investigate the relationship between markers of systemic inflammation (TNF-α, IL-6, IL-1ß, INF-γ, IL-2, IL-4, IL-10 and hsCRP) and cognitive function in 286 healthy volunteers aged 60-75 years. We assessed cognitive functioning across domains including attention, speed of memory, working memory and episodic memory using the Cognitive Drug Research test battery. Only IFN-γ was related to cognitive function, being associated with greater odds of having low continuity of attention (log2 IFN-γ OR, 1.46; 95 % CI, 1.18-1.85). The relationship between episodic memory, speed of memory and inflammation varied with BMI. In high BMI participants, increased inflammation was associated with worse cognitive function, while this association was reversed in those with low BMI. Outside of the influence of IFN-γ on attention, low-grade systemic inflammation was not robustly associated with cognitive function in this sample of middle to older aged healthy people. Further research is required to understand the role of BMI in the intersection of inflammation and cognitive function.

Four mutant alleles elucidate the role of the G2 protein in the development of C(4) and C(3) photosynthesizing maize tissues.

Maize leaf blades differentiate dimorphic photosynthetic cell types, the bundle sheath and mesophyll, between which the reactions of C(4) photosynthesis are partitioned. Leaf-like organs of maize such as husk leaves, however, develop a C(3) pattern of differentiation whereby ribulose bisphosphate carboxylase (RuBPCase) accumulates in all photosynthetic cell types. The Golden2 (G2) gene has previously been shown to play a role in bundle sheath cell differentiation in C(4) leaf blades and to play a less well-defined role in C(3) maize tissues. To further analyze G2 gene function in maize, four g2 mutations have been characterized. Three of these mutations were induced by the transposable element Spm. In g2-bsd1-m1 and g2-bsd1-s1, the element is inserted in the second intron and in g2-pg14 the element is inserted in the promoter. In the fourth case, g2-R, four amino acid changes and premature polyadenylation of the G2 transcript are observed. The phenotypes conditioned by these four mutations demonstrate that the primary role of G2 in C(4) leaf blades is to promote bundle sheath cell chloroplast development. C(4) photosynthetic enzymes can accumulate in both bundle sheath and mesophyll cells in the absence of G2. In C(3) tissue, however, G2 influences both chloroplast differentiation and photosynthetic enzyme accumulation patterns. On the basis of the phenotypic data obtained, a model that postulates how G2 acts to facilitate C(4) and C(3) patterns of tissue development is proposed.

The maize golden2 gene defines a novel class of transcriptional regulators in plants.

In the C4 plant maize, three photosynthetic cell types differentiate: C4 bundle sheath, C4 mesophyll, and C3 mesophyll cells. C3 mesophyll cells represent the ground state, whereas C4 bundle sheath and C4 mesophyll cells are specialized cells that differentiate in response to light-induced positional signals. The Golden2 (G2) gene regulates plastid biogenesis in all photosynthetic cells during the C3 stages of development. However, G2 function is specifically committed to the differentiation of bundle sheath cell chloroplasts in C4 leaf blades. In this article, we report the isolation of G2-like (Glk) genes from maize and rice, providing evidence for a family of Glk genes in plants. The expression profiles of the rice Glk genes suggest that these genes may act redundantly to promote photosynthetic development in this C3 species. In maize, G2 and ZmGlk1 transcripts accumulate primarily in C4 bundle sheath and C4 mesophyll cells, respectively, suggesting a specific role for each gene in C4 differentiation. We show that G2 and ZmGLK1 both can transactivate reporter gene transcription and dimerize in yeast, which supports the idea that these proteins act as transcriptional regulators of cell-type differentiation processes.

GOLDEN 2: a novel transcriptional regulator of cellular differentiation in the maize leaf.

The differentiation of distinct cell types within the leaf is essential for normal plant development. We characterized previously a transposon-induced mutant of maize (bundle sheath defective1) that disrupts the differentiation of a single photosynthetic cell type in the leaf. In this study, we show that this mutation is allelic to golden2 (g2), a lesion first reported 70 years ago. We cloned G2 by using Suppressor-mutator as a molecular tag. The gene encodes a 2. 2-kb transcript that is present throughout the wild-type leaf but is most abundant in C4 leaf blade tissue. Gene sequence data showed the existence of a bipartite nuclear localization signal encoded by the first exon, and we determined that G2 reporter gene fusions are targeted to the nucleus in onion epidermal cells. Further sequence analysis indicated the presence of a novel motif within the deduced protein sequence that shares features with TEA DNA binding domains. Therefore, we propose that G2 acts as a novel transcriptional regulator of cellular differentiation in the maize leaf.