Leaf abaxial and adaxial surfaces differentially affect the interaction of Botrytis cinerea across several eudicots.

Eudicot plant species have leaves with two surfaces: the lower abaxial and the upper adaxial surface. Each surface varies in a diversity of components and molecular signals, resulting in potentially different degrees of resistance to pathogens. We tested how Botrytis cinerea, a necrotroph fungal pathogen, interacts with the two different leaf surfaces across 16 crop species and 20 Arabidopsis genotypes. This showed that the abaxial surface is generally more susceptible to the pathogen than the adaxial surface. In Arabidopsis, the differential lesion area between leaf surfaces was associated with jasmonic acid (JA) and salicylic acid (SA) signaling and differential induction of defense chemistry across the two surfaces. When infecting the adaxial surface, leaves mounted stronger defenses by producing more glucosinolates and camalexin defense compounds, partially explaining the differential susceptibility across surfaces. Testing a collection of 96 B. cinerea strains showed the genetic heterogeneity of growth patterns, with a few strains preferring the adaxial surface while most are more virulent on the abaxial surface. Overall, we show that leaf-Botrytis interactions are complex with host-specific, surface-specific, and strain-specific patterns.

Diverse Allyl Glucosinolate Catabolites Independently Influence Root Growth and Development.

Glucosinolates (GSLs) are sulfur-containing defense metabolites produced in the Brassicales, including the model plant Arabidopsis (Arabidopsis thaliana). Previous work suggests that specific GSLs may function as signals to provide direct feedback regulation within the plant to calibrate defense and growth. These GSLs include allyl-GSL, a defense metabolite that is one of the most widespread GSLs in Brassicaceae and has also been associated with growth inhibition. Here we show that at least three separate potential catabolic products of allyl-GSL or closely related compounds affect growth and development by altering different mechanisms influencing plant development. Two of the catabolites, raphanusamic acid and 3-butenoic acid, differentially affect processes downstream of the auxin signaling cascade. Another catabolite, acrylic acid, affects meristem development by influencing the progression of the cell cycle. These independent signaling events propagated by the different catabolites enable the plant to execute a specific response that is optimal to any given environment.