A Holistic Approach to Analyze Systemic Jasmonate Accumulation in Individual Leaves of Arabidopsis Rosettes Upon Wounding

Abstract

Phytohormones, especially jasmonates, are known to be mediators of the plant responses to wounding and herbivore feeding. Their role in such stress responses has been largely studied locally in treated leaves. However, less is known about the induced systemic distribution of phytohormone signals upon these kinds of stresses. Here, a holistic approach was performed in order to investigate the systemic phytohormone pattern in the rosette of Arabidopsis thaliana after herbivore-related wounding. Levels of different stress-related phytohormones such as jasmonates, abscisic acid, and salicylic acid were analyzed in individual leaves. We demonstrate that the typically used sampling method, where leaves are first cut and immediately frozen, causes false-positive results since cutting already induces systemic jasmonate elevations within less than 1.6 min. Therefore, this approach is not suitable to study systemic phytohormone changes in the whole plant. By developing a new method where leaves are frozen first and subsequently cut, sampling-induced phytohormone elevations could be reduced. Using this new method, we show that jasmonic acid and its active isoleucine conjugate (jasmonoyl-isoleucine) are involved in the fast systemic wound response of Arabidopsis. A systemic induction of the jasmonates’ precursor, 12-oxo-phytodienoic acid, was not observed throughout our treatments. The systemic phytohormone distribution pattern is strongly linked to the vascular connections between the leaves, providing further evidence that the vascular system is used for long distance-signaling in Arabidopsis. Besides already known vascular connections, we also demonstrate that the systemic distribution of jasmonate signals can be extended to distant leaves, which are systemically but indirectly connected via another vascularly connected leaf. This holistic approach covering almost the whole Arabidopsis rosette introduces a method to overcome false-positive results in systemic phytohormone determinations and demonstrates that wounding-induced long-distance signaling includes fast changes in jasmonate levels in systemic, non-treated leaves.

Plant–Pathogen Interactions: Underestimated Roles of Phyto-oxylipins

“…Literature is replete with publications on oxylipins as signalling molecules in plant defence mechanisms and many studies provide evidence for a strong interplay between phytohormones [3,26,39,[49][50][51][52][53][54][55][56][57]. JA and its derivatives, known as jasmonates, are the best-characterised LOX-derived metabolites as they accumulate quickly in damaged plants [2,36,58].…”

“…Adapted from [4,16,17]. rapidly (<5 min) in leaves distal to wounding sites [30,50,61]. Interestingly, this long-distance signalling does not seem to involve the direct movement of hormones and could involve much faster systems: electrical coupling or ROS and Ca 2 +-mediated waves, 'trio signalling' [62,63].…”

Systemin‐mediated long‐distance systemic defense responses

“…, 2012; Heyer et al . , 2018; Schulze et al , 2019). Therefore, it is necessary to re‐quantify JA concentrations in these plants as both wounding and SYS treatment caused JA accumulation in tomato leaves as demonstrated previously (Doares et al .…”

“…(2013) and Heyer et al . (2018), who reported that OPDA concentrations increased only in local tissues but not in systemic leaves after continuous wounding. This suggested that the systemic elevation of JA is not a result of de novo biosynthesis, but rather of transport between the leaves, as shown in N. tabacum plants (Sato et al , 2011).…”

Specialized 16SrX phytoplasmas induce diverse morphological and physiological changes in their respective fruit crops

“…Phytohormone analysis was performed by LC-MS/MS as in Heyer et al . [ 87 ] on an Agilent 1260 series HPLC system (Agilent Technologies) with the modification that a tandem mass spectrometer QTRAP 6500 (SCIEX, Darmstadt, Germany) was used. Details of the instrument parameters and response factors for quantification can be found in S1 Table .…”