Misexpression of a Chloroplast Aspartyl Protease Leads to Severe Growth Defects and Alters Carbohydrate Metabolism in Arabidopsis    

Abstract

The crucial role of carbohydrate in plant growth and morphogenesis is widely recognized. In this study, we describe the characterization of nana, a dwarf Arabidopsis (Arabidopsis thaliana) mutant impaired in carbohydrate metabolism. We show that the nana dwarf phenotype was accompanied by altered leaf morphology and a delayed flowering time. Our genetic and molecular data indicate that the mutation in nana is due to a transfer DNA insertion in the promoter region of a gene encoding a chloroplast-located aspartyl protease that alters its pattern of expression. Overexpression of the gene (oxNANA) phenocopies the mutation. Both nana and oxNANA display alterations in carbohydrate content, and the extent of these changes varies depending on growth light intensity. In particular, in low light, soluble sugar levels are lower and do not show the daily fluctuations observed in wild-type plants. Moreover, nana and oxNANA are defective in the expression of some genes implicated in sugar metabolism and photosynthetic light harvesting. Interestingly, some chloroplast-encoded genes as well as genes whose products seem to be involved in retrograde signaling appear to be down-regulated. These findings suggest that the NANA aspartic protease has an important regulatory function in chloroplasts that not only influences photosynthetic carbon metabolism but also plastid and nuclear gene expression.

Ubiquitin-Proteasome Dependent Regulation of the GOLDEN2-LIKE 1 Transcription Factor in Response to Plastid Signals

“…Because we routinely supply Suc to MS plates, we suspected that Suc may up-regulate the expression of GLK1. Consistent with this idea, it has been shown that carbohydrate metabolism in chloroplasts affects the expression of GLK1 in the nucleus (Paparelli et al, 2012). Hence, we tested the effect of Suc on the accumulation of GLK1.…”

Nighttime Sugar Starvation Orchestrates Gibberellin Biosynthesis and Plant Growth in Arabidopsis

“…Total RNA Extraction and Quantitative PCR RNA extraction, removal of genomic DNA, cDNA synthesis, and quantitative RT-PCR analyses were performed as described previously (Paparelli et al, 2012). GAPDH and 40SrRNA were used as reference genes.…”

“…Frozen samples were homogenized then extracted in perchloric acid, as previously described (Paparelli et al, 2012). Glc, Suc, Fru, and starch were measured enzymatically on the neutralized supernatant (soluble sugars) (Guglielminetti et al, 1995) and the insoluble pellet (starch) (Critchley et al, 2001).…”

Two-dimensional zymography in detection of proteolytic enzymes in wheat leaves

“…Type II metacaspase from wheat leaves (TaeMCAII) was modeled in silico, cloned and characterized (Piszczek et al 2011;Piszczek et al 2012). Studies of Arabidopsis thaliana dwarf mutant, impaired in carbohydrate metabolism, enabled characterization of NANA, chloroplastlocated, aspartic proteinase (Paparelli et al 2012).…”