FIBRILLIN4Is Required for Plastoglobule Development and Stress Resistance in Apple and Arabidopsis

Abstract

The fibrillins are a large family of chloroplast proteins that have been linked with stress tolerance and disease resistance. FIBRILLIN4 (FIB4) is found associated with the photosystem II light-harvesting complex, thylakoids, and plastoglobules, which are chloroplast compartments rich in lipophilic antioxidants. For this study, FIB4 expression was knocked down in apple (Malus 3 domestica) using RNA interference. Plastoglobule osmiophilicity was decreased in fib4 knockdown (fib4 KD) tree chloroplasts compared with the wild type, while total plastoglobule number was unchanged. Compared with the wild type, net photosynthetic CO 2 fixation in fib4 KD trees was decreased at high light intensity but was increased at low light intensity. Furthermore, fib4 KD trees produced more anthocyanins than the wild type when transferred from low to high light intensity, indicating greater sensitivity to high light stress. Relative to the wild type, fib4 KD apples were more sensitive to methyl viologen and had higher superoxide levels during methyl viologen treatment. Arabidopsis (Arabidopsis thaliana) fib4 mutants and fib4 KD apples were more susceptible than their wild-type counterparts to the bacterial pathogens Pseudomonas syringae pathovar tomato and Erwinia amylovora, respectively, and were more sensitive to ozone-induced tissue damage. Following ozone stress, plastoglobule osmiophilicity decreased in wild-type apple and remained low in fib4 KD trees; total plastoglobule number increased in fib4 KD apples but not in the wild type. These results indicate that FIB4 is required for plastoglobule development and resistance to multiple stresses. This study suggests that FIB4 is involved in regulating plastoglobule content and that defective regulation of plastoglobule content leads to broad stress sensitivity and altered photosynthetic activity.

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.…”

“…It has been suggested that FBN4, with its lipocalin domain, is involved in the transport of PQ-9 and other molecules from the thylakoids to the plastoglobules (Singh et al, 2010(Singh et al, , 2012. However, the precise biological functions of the fibrillins require further investigation.…”

“…Furthermore, the overexpression of a pepper fibrillin in tobacco (Nicotiana tabacum) increased the numbers of plastoglobules (Rey et al, 2000). In addition to their structural roles, fibrillins are involved in photosynthesis during plant development, tolerance of photooxidative stress, and resistance to biotic stress (Rey et al, 2000;Leitner-Dagan et al, 2006;Simkin et al, 2007;Cunningham et al, 2010;Singh et al, 2010;Singh and McNellis, 2011). Recently, fibrillin mutants of Arabidopsis have extended our understanding of the functions of the fibrillin proteins.…”

Pathogenicity and infection strategies of the fire blight pathogen Erwinia amylovora in Rosaceae: State of the art

“…Both and Baldo et al (2010) noticed an induction of some photosynthetic genes during a Malus-E. amylovora interaction. Research by Singh et al (2010) suggested that FIBRILLIN4, which is associated with photosystem II, could also play a part in fire blight infections, as the disease is more expressed in the knockdown mutant.…”

The Functional Network of the Arabidopsis Plastoglobule Proteome Based on Quantitative Proteomics and Genome-Wide Coexpression Analysis

“…Their shrinking and swelling in response to (a)biotic stresses and during developmental transitions, as well as in plastid biogenesis mutants, are well documented (Gaude et al, 2007;Simkin et al, 2007;Singh et al, 2010;Zhang et al, 2010). Recent results suggest that PGs are involved in active channeling of hydrophobic metabolites between the thylakoid and PG, permitted by the contiguous association of the two structures Gaude et al, 2007).…”