Physiological responses of Catharanthus roseus (periwinkle) to ash yellows phytoplasmal infection

Abstract

Summary• Photosynthetic responses of periwinkle ( Catharanthus roseus ) were compared during disease development after infection by two strains of ash yellows (AshY) phytoplasmas that differed in aggressiveness.• Healthy plants were inoculated by grafting with diseased scions. Mature leaves formed before grafting of diseased scion, and leaves formed during disease development were monitored for physiological changes.• Leaves formed before inoculation remained visually and physiologically asymptomatic until normal senescence. However, leaves formed after inoculation had reduced photosynthesis, due to reductions in both the maximum carboxylation rate ( Vc max ) and noncyclic electron transport ( J max ). In these leaves, photoinhibition resulted from photoprotective processes rather than photooxidative damage to PSII reaction centres. Stomatal conductance ( G s ) was reduced, but this did not increase the stomatal limitation to photosynthesis. Changes in G s were not correlated with changes in leaf ABA concentration.• Known differences in phytoplasmal aggressiveness were correlated with degrees of inhibition of photosynthesis and occurence of photoinhibition. AshY phytoplasmas appear to cause metabolic perturbations associated with localized accumulation or multiplication of the pathogen in symptomatic leaves. Key words: Catharanthus roseus

Analysis of phytoplasma-responsive sRNAs provide insight into the pathogenic mechanisms of mulberry yellow dwarf disease

“…Therefore, it is more likely that the phytoplasma infection-induced alteration in hormonal signaling triggers reprogramming of the plant growth and developmental pattern, leading to some symptoms in infected plants. This is in accord with early reports that phytoplasma infection disturbs hormonal balance in the host plants433343536.…”

cDNA-AFLP analysis of gene expression changes in apple trees induced by phytoplasma infection during compatible interaction

“…These may explain the different results in the expression patterns of some genes obtained by AFLP and qRT-PCR. As reported by Tan and Whitlow (2001), leaves formed before inoculation remained visually and physiologically asymptomatic, this phenomenon can also explain the differences obtained in this research for the gene expression patterns between symptomatic and nonsymptomatic samples.…”

Flavescence dorée phytoplasma deregulates stomatal control of photosynthesis in Vitis vinifera

“…In addition, subsequent blocks in sugar and protein translocation are followed by an increase of starch in source leaves and a decrease in sink leaves and roots as previously observed in coconut palms affected by lethal yellowing (Maust et al, 2003) and in maize plants affected by bushy stunt (Junqueira et al, 2004). Additionally, a related decrease in chlorophyll content and chlorophyll biosynthesis has been observed in coconut palms affected by coconut lethal yellowing (Leon et al, 1996), in apple trees affected by apple proliferation (Bertamini et al, 2002a) and periwinkles affected by ash yellows (Tan & Whitlow, 2001).…”

“…Currently, the key ecophysiological leaf traits related to phytoplasma disease symptoms are decreased rates of gas exchange variables: carbon assimilation (A) and water transpiration (E) (Tan & Whitlow, 2001;Endeshaw et al, 2012). Proposed mechanisms leading to stomatal closure were related to an increase in abscisic acid (ABA) concentration (Leon et al, 1996;Martinez et al, 2000) and sucrose accumulation around guard cells, as reported by Lu et al (1997).…”