Tonoplast-associated calcium signaling regulates manganese homeostasis in Arabidopsis

Abstract

Manganese (Mn) is an essential micronutrient in plants. However, excessive Mn absorption in acidic and waterlogged soils can lead to Mn toxicity. Despite their essential roles in Mn homeostasis, transcriptional and post-transcriptional modifications of Mn transporters remain poorly understood. Here, we demonstrated that high-Mn stress induces an obvious Ca 2+ signature in Arabidopsis. We identified four calcium-dependent protein kinases, CPK4/5/6/11, that interact with the tonoplast-localized Mn and iron (Fe) transporter MTP8 in vitro and in vivo. The cpk4/5/6/11 quadruple mutant displayed a dramatic high-Mn-sensitive phenotype similar to that of the mtp8 mutant. CPKs phosphorylated the N-terminal domain of MTP8 primarily at the Ser31 and Ser32 residues. Transport assays combined with multiple physiological experiments on phospho-dead variant MTP8 S31/32A and phospho-mimetic variant MTP8 S31/32D plants under different Mn and Fe conditions suggested that Ser31 and Ser32 are crucial for MTP8 function. In addition, genetic analysis showed that CPKs functioned upstream of MTP8. In summary, we identified a tonoplastassociated calcium signaling cascade that orchestrates Mn homeostasis and links Mn toxicity, Ca 2+ signaling, and Mn transporters. These findings provide new insight into Mn homeostasis mechanisms and Ca 2+ signaling pathways in plants, providing potential targets for engineering heavy metal toxicitytolerant plants.

Identification of Potential Gene Regulatory Pathways Affecting the Ratio of Four-Seed Pod in Soybean

“…Preventing the interference of pathogens from the outside is the prerequisite for healthy growth of plants. Moreover, calcium can promote the growth of root hairs ( Zhang et al, 2021 ). In our study, these calcium-binding genes showed high expression characteristics in roots, indicating that plants with vigorous roots could absorb more nutrients and thus contribute to the accumulation of nutrients by the aboveground leaves, flowers, and pods.…”

“…The high level of ABA in the kernels or pods can affect the abortion of young ovaries by inhibiting cell division ( Dembinska et al, 1992 ; Setter and Flannigan, 2001 ; Liu et al, 2003 ). Calcium is an essential nutrient element in the process of plant growth and development, which is mainly transported from the roots to aboveground leaves through the xylem ( Zhang et al, 2021 ). A lack of calcium caused empty pods in peanut ( Yang et al, 2020 ).…”

“…A lack of calcium caused empty pods in peanut ( Yang et al, 2020 ). Calcium has been shown to not only enhance the nutrients accumulation but also activate the hormone-related signaling pathway such as ABA signals in the development of plants ( Yang et al, 2017 ; Zhang et al, 2021 ). Although root-derived ABA and calcium signaling regulatory pathways can be involved in the formation of crop pods, their influence on the ratio of soybean four-seed pod under natural conditions has not been reported yet.…”

Overexpression of METAL TOLERANCE PROTEIN8 reveals new aspects of metal transport in Arabidopsis thaliana seeds

“…Cell type-specific targeting and function may be brought about by essential interacting proteins only present in the respective cell types. One class of interacting proteins are protein kinases, and the regulation of MTP8 by phosphorylation has recently been shown(Zhang et al 2021). It still needs to be established if such potential mechanisms regulate MTP8 in Arabidopsis seeds.…”

GTPase ROP6 negatively modulates phosphate deficiency through inhibition of PHT1;1 and PHT1;4 in Arabidopsis thaliana

“…For construction of pull-down vectors, the full-length ORFs of ROP6 and the truncated PHT1 genes (PHT1;1-C 504-524AA , PHT1;4-C 504-534AA ) were amplified and subcloned into the pMAL-C2X and pGEX4T-1 vectors, respectively. The pull-down assay was performed as described (Zhang et al, 2021). ROP6 activity assay was performed as previously described (Han et al, 2018).…”