Plant lipid‐associated fibrillin proteins condition jasmonate production under photosynthetic stress

Abstract

SUMMARYThe role of a subfamily of lipid globule-associated proteins, referred to as plant fibrillins (FIB1a, -1b, -2), was determined using a RNA interference (RNAi) strategy. We show that Arabidopsis plants with reduced levels of these plastid structural proteins are impaired in long-term acclimation to environmental constraint, namely photooxidative stress imposed by high light combined with cold. As a result, their photosynthetic apparatus is inefficiently protected. This leads to the prevalence of an abnormal granal and stromal membrane arrangement, as well as higher photosystem II photoinhibition under stress. The visible phenotype of FIB1-2 RNAi lines also includes retarded shoot growth and a deficit in anthocyanin accumulation under stress. All examined phenotypic effects of lower FIB levels are abolished by jasmonate (JA) treatment. An atypical expression pattern of several JA-induced genes was observed in RNAi plants. A JA-deficient mutant was found to share similar stress phenotypic characteristics with FIB RNAi plants. We conclude a new physiological role for JA, namely acclimation of chloroplasts, and that light/cold stress-related JA biosynthesis is conditioned by the accumulation of plastoglobule-associated FIB1-2 proteins. Consistent correlative data suggest that this FIB effect is mediated by plastoglobule (and triacylglycerol) accumulation as the potential site for initiating the chloroplast stress-related JA biosynthesis.

Fibrillin 5 Is Essential for Plastoquinone-9 Biosynthesis by Binding to Solanesyl Diphosphate Synthases in Arabidopsis

“…FBN5 is a phylogenetically distant relative of other fibrillins in Arabidopsis (Singh and McNellis, 2011), and it localizes to the stroma, with a lower pI and lower hydrophobicity than the other fibrillins (Lundquist et al, 2012). Therefore, FBN5 may play different roles from those previously reported for the fibrillins that localize primarily to the plastoglobules (Trebst, 1978;Yang et al, 2006;Singh et al, 2010Singh et al, , 2012Youssef et al, 2010). Surprisingly, we found that FBN5 specifically interacts with two solanesyl diphosphate synthases, SPS1 and SPS2, in the chloroplasts.…”

“…Recently, fibrillin mutants of Arabidopsis have extended our understanding of the functions of the fibrillin proteins. The Arabidopsis FIBRILLIN1 (FBN1) gene family is involved in abscisic acid-mediated protection from photoinhibition (Yang et al, 2006), and the FBN1 and FBN2 gene families modulate jasmonate biosynthesis during light and cold stress (Youssef et al, 2010).…”

Proteome Analysis of Cytoplasmatic and Plastidic β-Carotene Lipid Droplets in Dunaliella bardawil

“…In contrast to plant and green algae such as C. reinhardtii, in which fibrillins are the major lipidassociated proteins (Ytterberg et al, 2006;Singh and McNellis, 2011;Lundquist et al, 2012b), in the D. bardawil proteome they are minor constituents compared with CGP. In earlier work, we found that proteolysis of CGP destabilizes bC-plastoglobuli, suggesting that CGP may have a similar role to fibrillins in stabilizing the plastoglobules (Katz et al, 1995;Youssef et al, 2010;Singh and McNellis 2011). We did not identify in our proteomes homologs of green algal oleosins (Huang et al, 2013), Chlorella spp.…”

A mechanism implicating plastoglobules in thylakoid disassembly during senescence and nitrogen starvation

“…In addition, the number of PG is lower in fib1-2 RNAi plants than in wild type plants, concomitant with a reduction of TAGs in PG that makes less C18:3 fatty acid, the precursor of jasmonate, available in plastids. Indeed, the fibrillins in PG could influence early steps of jasmonate synthesis during stress (Youssef et al 2010).…”