Boron Deficiency Increases Cytosolic Ca2+ Levels Mainly via Ca2+ Influx from the Apoplast in Arabidopsis thaliana Roots

Abstract

Boron (B) is a micronutrient for plant development, and its deficiency alters many physiological processes. However, the current knowledge on how plants are able to sense the B-starvation signal is still very limited. Recently, it has been reported that B deprivation induces an increase in cytosolic calcium concentration ([Ca2+]cyt) in Arabidopsis thaliana roots. The aim of this work was to research in Arabidopsis whether [Ca2+]cyt is restored to initial levels when B is resupplied and elucidate whether apoplastic Ca2+ is the major source for B-deficiency-induced rise in [Ca2+]cyt. The use of chemical compounds affecting Ca2+ homeostasis showed that the rise in root [Ca2+]cyt induced by B deficiency was predominantly owed to Ca2+ influx from the apoplast through plasma membrane Ca2+ channels in an IP3-independent manner. Furthermore, B resupply restored the root [Ca2+]cyt. Interestingly, expression levels of genes encoding Ca2+ transporters (ACA10, plasma membrane PIIB-type Ca2+-ATPase; and CAX3, vacuolar cation/proton exchanger) were upregulated by ethylene glycol tetraacetic acid (EGTA) and abscisic acid (ABA). The results pointed out that ACA10, and especially CAX3, would play a major role in the restoration of Ca2+ homeostasis after 24 h of B deficiency.

Genome-Wide Identification of Long Non-coding RNA in Trifoliate Orange (Poncirus trifoliata (L.) Raf) Leaves in Response to Boron Deficiency

“…At the cellular level, B deficiency increases cytosolic Ca 2+ levels in Arabidopsis thaliana roots and promotes tobacco BY-2 cells to take up more Ca 2+ than control cells [44,45]. A recent study demonstrated that B deficiency increases cytosolic Ca 2+ levels mainly via Ca 2+ influx from the apoplasts in Arabidopsis thaliana roots [46]. At the molecular level, the expression of Ca 2+ -related genes in these Arabidopsis thaliana roots significantly increased under B deficiency conditions [45].…”

Role of boron and its interaction with other elements in plants

“…Another study performed in tobacco plants shows that short-term B deficiency is related with the influx of Ca 2+ ions and the expression of WIPK and WIZZ, associated with BY-2 cells and pectin network structure (Koshiba et al, 2009). A more recent study by Quiles-Pando et al (2019), supports the idea that B deficiency regulates the expression of Ca 2+ transporter genes such as CNGC19, ACA and CAX3, triggering an increase in the Ca 2+ concentration in the cytoplasm. This might be attributed to the expression of Ca 2+ transporters in an attempt to regulate Ca 2+ homeostasis based on a response due to B deficiency.…”

Carbon-11 Radiotracing Reveals Physiological and Metabolic Responses of Maize Grown under Different Regimes of Boron Treatment

“…The results obtained for 0 mM BA maize leaves were in line with prior results reported for boron-deficient tobacco leaves [ 83 ] and with results from boron-toxic maize leaves [ 38 ]. It is interesting to note that calcium has been reported to be associated with sensing boron deficiency in plants and that calcium levels increased in boron-deficient tobacco BY-2 cells [ 84 ], Arabidopsis roots [ 85 , 86 ], and Malus domestica pollen tips [ 87 ]. These contrasting results could imply that calcium is not involved in a process sensing boron in leaves in maize.…”