Evolution of the life cycle in land plants

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92043/1/j.1759-6831.2012.00188.x.pd

Cell autonomous and non-autonomous functions of plant intracellular immune receptors in stomatal defense and apoplastic defense.

Stomatal closure defense and apoplastic defense are two major immunity mechanisms restricting the entry and propagation of microbe pathogens in plants. Surprisingly, activation of plant intracellular immune receptor NLR genes, while enhancing whole plant disease resistance, was sometimes linked to a defective stomatal defense in autoimmune mutants. Here we report the use of high temperature and genetic chimera to investigate the inter-dependence of stomatal and apoplastic defenses in autoimmunity. High temperature inhibits both stomatal and apoplastic defenses in the wild type, suppresses constitutive apoplastic defense responses and rescues the deficiency of stomatal closure response in autoimmune mutants. Chimeric plants have been generated to activate NLR only in guard cells or the non-guard cells. NLR activation in guard cells inhibits stomatal closure defense response in a cell autonomous manner likely through repressing ABA responses. At the same time, it leads to increased whole plant resistance accompanied by a slight increase in apoplastic defense. In addition, NLR activation in both guard and non-guard cells affects stomatal aperture and water potential. This study thus reveals that NLR activation has a differential effect on immunity in a cell type specific matter, which adds another layer of immune regulation with spatial information

Data from: Systematic assessment of retrieval methods for canopy far-red solar-induced chlorophyll fluorescence (SIF) using automated high-frequency field spectroscopy

Christine Y. Chang, Jeffrey Melkonian, Susan J. Riha, Christian Frankenberg, Luis Guanter, Lianhong Gu, Ying Sun. (2020) Data from: Systematic assessment of retrieval methods for canopy far-red solar-induced chlorophyll fluorescence (SIF) using automated high-frequency field spectroscopy. [dataset] Cornell University Library eCommons Repository. https://doi.org/10.7298/wqx5-ba07Data in support of the following research: Remote sensing of solar-induced chlorophyll fluorescence (SIF) offers potential to infer photosynthesis across scales and biomes. Many retrieval methods have been developed to estimate top-of-canopy SIF using ground-based spectroscopy. However, inconsistencies among methods may confound interpretation of SIF dynamics, eco-physiological/environmental drivers, and its relationship with photosynthesis. Using high temporal- and spectral-resolution ground-based spectroscopy, we aimed to 1) evaluate performance of SIF retrieval methods under diverse sky conditions using continuous field measurements; 2) assess method sensitivity to fluctuating light, reflectance and fluorescence emission spectra; and 3) inform users for optimal ground-based SIF retrieval. Analysis included field measurements from bi-hemispherical and hemispherical-conical systems and synthetic upwelling radiance constructed from measured downwelling radiance, simulated reflectance and simulated fluorescence for benchmarking. Fraunhofer-based differential optical absorption spectroscopy (DOAS) and singular vector decomposition (SVD) retrievals exhibit convergent SIF-PAR relationships and diurnal consistency across different sky conditions while O2A-based spectral fitting method (SFM), SVD, and modified Fraunhofer line discrimination (3FLD) exhibit divergent SIF-PAR relationships across sky conditions. Such behavior holds across system configurations, though hemispherical-conical systems diverge less across sky conditions. O2A retrieval accuracy, influenced by atmospheric distortion, improves with a narrower fitting window and when training SVD with temporally-local spectra. This may impact SIF-photosynthesis relationships interpreted by previous studies using O2A-based retrievals with standard (759-767.76 nm) fitting windows. Fraunhofer-based retrievals resist atmospheric impacts but are noisier and more sensitive to assumed SIF spectral shape than O2A-based retrievals. We recommend SVD or SFM using reduced fitting window (759.5-761.5 nm) for robust far-red SIF retrievals across sky conditions

Occurrence of loroxanthin, loroxanthin decenoate, and loroxanthin dodecenoate in tetraselmis species (prasinophyceae, chlorophyta)

9 páginas, 5 tablas, 2 figurasThe pigment composition of six species of Tetraselmis (Prasinophyceae) was analyzed using improved HPLC methods. All pigment extracts showed three peaks corresponding to unknown carotenoids. The isolated pigments were analyzed using UV–Vis spectroscopy, electrospray ionization–mass spectrometry (ESI–MS), and when carotenoid esters were suspected, gas chromatography–mass spectrometry (GC–MS) of the methyl ester and dimethyloxazoline derivative of the corresponding fatty acid. The new pigments were determined to be loroxanthin, loroxanthin 19-(2-decenoate), and loroxanthin 19-(2-dodecenoate); this is the first time these pigments have been described in the genus Tetraselmis. Moreover, this is the first report of esterification of 2-decenoic acid to loroxanthin. The relative contents of these pigments depended on the light regime, with the lowest proportions measured at the highest photon flux density assayed. The implications of the identification of these pigments in the genus Tetraselmis for the pigment types previously described in the class Prasinophyceae are discussedThis work was supported by Xunta de Galicia through project PGIDT99MAR50102.Peer reviewe