The Over-expression of the Plastidial Transglutaminase from Maize in Arabidopsis Increases the Activation Threshold of Photoprotection

Abstract

Plastidial transglutaminase is one of the most promising enzymes in chloroplast bioenergetics due to its link with polyamine pathways and the cross talk with signals such as Ca2+ and GTP. Here, we show the effect of the increase of transglutaminase activity in Arabidopsis by using genetic transformation techniques. These lines fulfill their biological cycle normally (normal growth in soil, production of viable seeds) and show a relatively mild increase in transglutaminase activity (127%). These overexpressors of transglutaminase (OE TGase) have an extended stroma thylakoid network (71% higher number of PSIIβ centers), similar chlorophyll content (-4%), higher linear electron flow (+13%), and higher threshold of photoprotection activation (∼100%). On the other hand OE TGase showed a reduced maximum photochemistry of PSII (-6.5%), a smaller antenna per photosystem II (-25%), a lower photoprotective “energization” quenching or qE (-77% at 490 μmol photons m-2 s-1) due to a higher threshold of qE activation and slightly lower light induced proton motive force (-17%). The role of the polyamines and of the transglutaminase in the regulation of chemiosmosis and photoprotection in chloroplasts is discussed.

Magnesium uptake by connecting fluid-phase endocytosis to an intracellular inorganic cation filter

“…When Mg 2+ is scarce but fully bioavailable, a condition that we mimicked through Mg 2+ -depleted but EDTA-free medium, the high-affinity Mg 2+ -transporters in the plasma membrane suffice to support growth. The endocytosis/polyP-dependent EAPEC route becomes essential for growth when bioavailability is low, enabling the cell to cope with this condition, which is often encountered in natural settings 5 .…”

“…This is especially the case for unicellular organisms with limited spatial motility such as yeast. Yeast species are found on plants and in soil 1 , habitats known to be rich in chelating agents like organic acids and tannins, which can limit the fraction of metal ions that are available for uptake across membranes 2 – 5 . Since plasma membrane metal transporters need free ions for uptake, mitigating strategies for metal acquisition in environments with low metal bioavailability would prove beneficial.…”

Polyamine Catabolism in Plants: A Universal Process With Diverse Functions

“…Biochemical effects of PAs have been unraveled in many physiological processes, primarily in stability and function of proteins and nucleic acids (Handa et al., 2018), partly due to their positive charge that enables them to electrostatically interact with polyanionic molecules inside the cell. Polyamines correlate with numerous vital biochemical functions, including protein regulation (Takahashi and Kakehi, 2010; Sayas et al., 2019), regulation of chemiosmosis and photoprotection in chloroplasts (Ioannidis et al., 2016), ATP synthesis (Ioannidis et al., 2006), ion channeling (Pottosin et al., 2014a; Shabala et al., 2016), membrane fluidity (Paschalidis et al., 2010; Bleackley et al., 2014; Shabala et al., 2016; Dorighetto Cogo et al., 2018), and control of N/C balance (Moschou et al., 2012; Gupta et al., 2013; Majumdar et al., 2016). Exogenous PA application enhanced plant tolerance/resistance to several abiotic stress conditions, such as salinity, drought, water logging/flooding, osmotic stress, heavy metals, and extreme temperatures (Liu et al., 2006, 2015; Moschou et al., 2008c, 2012; Paschalidis et al., 2009a; Toumi et al., 2010; Moschou and Roubelakis-Angelakis, 2014; Gupta et al., 2016; Handa et al., 2018; Nguyen et al., 2018; Tiburcio and Alcazar, 2018; Pal et al., 2019; Yin et al., 2019).…”

Genome-Wide Identification of Seven Polyamine Oxidase Genes in Camellia sinensis (L.) and Their Expression Patterns Under Various Abiotic Stresses

“…They play a vital role in flowering and development ( Ahmed et al, 2017 ), leaf development and senescence ( Sobieszczuk-Nowicka et al, 2015 ; Sobieszczuk-Nowicka, 2017 ), and fruit development and maturity ( Liu and Moriguchi, 2007 ; Fortes and Agudelo-Romero, 2018 ). In addition, PAs are key components of plant abiotic stress responses ( Liu et al, 2015 ; Montilla-Bascon et al, 2017 ), and their response mechanisms include participation in protein regulation ( Sayas et al, 2019 ), regulation of chemical penetration and photoprotection of chloroplasts ( Ioannidis et al, 2016 ), and control of N/C balance in plants ( Moschou et al, 2012 ). Furthermore, many studies have shown that the application of exogenous PAs enhanced the tolerance of plants to several abiotic stresses such as saline, drought, water logging, osmosis, heavy metals, and extreme temperatures ( Alcazar et al, 2006 ; Handa and Mattoo, 2010 ; Ogawa and Mitsuya, 2011 ; Nambeesan et al, 2012 ; Pál et al, 2019 ; Yin et al, 2019 ).…”