Plastids Are Major Regulators of Light Signaling in Arabidopsis    

Abstract

We previously provided evidence that plastid signaling regulates the downstream components of a light signaling network and that this signal integration coordinates chloroplast biogenesis with both the light environment and development by regulating gene expression. We tested these ideas by analyzing light-and plastid-regulated transcriptomes in Arabidopsis (Arabidopsis thaliana). We found that the enrichment of Gene Ontology terms in these transcriptomes is consistent with the integration of light and plastid signaling (1) down-regulating photosynthesis and inducing both repair and stress tolerance in dysfunctional chloroplasts and (2) helping coordinate processes such as growth, the circadian rhythm, and stress responses with the degree of chloroplast function. We then tested whether factors that contribute to this signal integration are also regulated by light and plastid signals by characterizing T-DNA insertion alleles of genes that are regulated by light and plastid signaling and that encode proteins that are annotated as contributing to signaling, transcription, or no known function. We found that a high proportion of these mutant alleles induce chloroplast biogenesis during deetiolation. We quantified the expression of four photosynthesis-related genes in seven of these enhanced deetiolation (end) mutants and found that photosynthesis-related gene expression is attenuated. This attenuation is particularly striking for Photosystem II subunit S expression. We conclude that the integration of light and plastid signaling regulates a number of END genes that help optimize chloroplast function and that at least some END genes affect photosynthesis-related gene expression.

Influence of plastids on light signalling and development

“…Thus, the nature of cry1 signalling is influenced by cellular context. Although cry1 was a positive regulator of other PhANGs besides Lhcb1 regardless of whether chloroplast biogenesis was blocked [5], blocking chloroplast biogenesis severely attenuated the light-induced expression of other PhANGs [57]. gun1 cry1 and gun1 hy5 synergistically attenuated the plastid regulation of Lhcb genes and chloroplast biogenesis, consistent with the integration of light and plastid-to-nucleus signalling [5].…”

Arabidopsis COP1 and SPA Genes Are Essential for Plant Elongation But Not for Acceleration of Flowering Time in Response to a Low Red Light to Far-Red Light Ratio

“…cop1-4 (McNellis et al, 1994), hy5-215 (Oyama et al, 1997), hy5-51 (Ruckle et al, 2007(Ruckle et al, , 2012, and hfr1-101 (Fankhauser and Chory, 2000) have been described earlier. The spa1-7 spa3-1 spa4-1 hfr1-101 and spa1-7 spa3-1 spa4-1 hy5-51 mutants were selected from the respective F2 populations based on phenotype and subsequently confirmed using polymorphic markers (Laubinger and Hoecker, 2003;Fittinghoff et al, 2006).…”

Roles for Light, Energy, and Oxygen in the Fate of Quiescent Axillary Buds

“…Nearly all of the top 50 most similar of 3,020 Perturbation studies attended to postgermination photomorphogenesis. Each of the top five most similar were wild-type studies that investigated light signaling and contrasted light conditions against continuous darkness (Supplemental Table S3B), for example, the role of plastid biogenesis in mediating light-dependent signaling (GEO accession GSE24517; Ruckle et al, 2012) and the role of light-dependent translational regulation in photomorphogenesis (GEO accession GSE29657; Liu Abbreviations not defined in the text: a1,4G, a-1,4-GLUCO-SIDASE; BCAAs, branched-chain amino acids; BCAT, BRANCHED-CHAIN AMINO ACID AMINOTRANSFERASE; Epi, ALDOSE 1-EPIMERASE; FBP, FRUCTOSE 1,6-BISPHOSPHATASE; FBPA, FRUCTOSE-BISPHOSPHATE ALDOLASE; G3PDH, GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE B; ME, NADP-DEPENDENT MALIC ENZYME; PEPC, PHOS-PHOENOLPYRUVATE CARBOXYKINASE; Rubisco, RIBULOSE BISPHOSPHATE CARBOXYLASE; SUS, SUCROSE SYN-THASE; TP, TREHALOSE-PHOSPHATASE. et al, 2012).…”