CDC48B facilitates the intercellular trafficking of SHORT-ROOT during radial patterning in roots

CDC48 in plants and its emerging function in plant immunity

Protein homeostasis, namely the balance between protein synthesis and degradation, must be finely controlled to ensure cell survival, notably through the ubiquitin-proteasome system (UPS). In all species, including plants, homeostasis is disrupted by biotic and abiotic stresses. A key player in the maintenance of protein balance, the protein CDC48, shows emerging functions in plants, particularly in response to biotic stress. In this review on CDC48 in plants, we detail its highly conserved structure, describe a gene expansion that is only present in Viridiplantae, discuss its various functions and regulations, and finally highlight its recruitment, still not clear, during the plant immune response.

CDC48A, an interactor of WOX2, is required for embryonic patterning in Arabidopsis thaliana

KEY MESSAGE

Interactor of WOX2, CDC48A, is crucial for early embryo patterning and shoot meristem stem cell initiation, but is not required for WOX2 protein turnover or subcellular localization. During Arabidopsis embryo patterning, the WUSCHEL HOMEOBOX 2 (WOX2) transcription factor is a major regulator of protoderm and shoot stem cell initiation. Loss of WOX2 function results in aberrant protodermal cell divisions and, redundantly with its paralogs WOX1, WOX3, and WOX5, compromised shoot meristem formation. To elucidate the molecular basis for WOX2 function, we searched for protein interactors by IP-MS/MS from WOX2-overexpression roots displaying reprogramming toward shoot-like cell fates. Here, we report that WOX2 directly interacts with the type II AAA ATPase molecular chaperone CELL DIVISION CYCLE 48A (CDC48A). We confirmed this interaction with bimolecular fluorescence complementation and co-immunoprecipitation and found that both proteins co-localize in the nucleus. We show that CDC48A loss of function results in protoderm and shoot meristem stem cell initiation defects similar to WOX2 loss of function. We also provide evidence that CDC48A promotes WOX2 activity independently of proteolysis or the regulation of nuclear localization, common mechanisms of CDC48A function in other processes. Our results point to a new role of CDC48A in potentiating WOX2 function during early embryo patterning.

Genetic dissection of ten photosynthesis-related traits based on InDel- and SNP-GWAS in soybean

KEY MESSAGE

A total of 416 InDels and 112 SNPs were significantly associated with soybean photosynthesis-related traits. GmIWS1 and GmCDC48 might be related to chlorophyll fluorescence and gas-exchange parameters, respectively. Photosynthesis is one of the main factors determining crop yield. A better understanding of the genetic architecture for photosynthesis is of great significance for soybean yield improvement. Our previous studies identified 5,410,112 single nucleotide polymorphisms (SNPs) from the resequencing data of 219 natural soybean accessions. Here, we identified 634,106 insertions and deletions (InDels) from these 219 accessions and used these InDel variations to perform principal component and linkage disequilibrium analysis of this population. The genome-wide association study (GWAS) were conducted on six chlorophyll fluorescence parameters (chlorophyll content, light energy absorbed per reaction center, quantum yield for electron transport, probability that a trapped exciton moves an electron into the electron transport chain beyond primary quinone acceptor, maximum quantum yield of photosystem II primary photochemistry in the dark-adapted state, performance index on absorption basis) and four gas-exchange parameters (intercellular carbon dioxide concentration, stomatal conductance, net photosynthesis rate, transpiration rate) and revealed 416 significant InDels and 112 significant SNPs. Based on GWAS results, GmIWS1 (encoding a transcription elongation factor) and GmCDC48 (encoding a cell division cycle protein) with the highest expression in the mapping region were determined as the candidate genes responsible for chlorophyll fluorescence and gas-exchange parameters, respectively. Further identification of favorable haplotypes with higher photosynthesis, seed weight and seed yield were carried out for GmIWS1 and GmCDC48. Overall, this study revealed the natural variations and candidate genes underlying the photosynthesis-related traits based on abundant phenotypic and genetic data, providing valuable insights into the genetic mechanisms controlling photosynthesis and yield in soybean.

Heavy Metal-Associated Isoprenylated Plant Proteins (HIPPs) at Plasmodesmata: Exploring the Link between Localization and Function

Heavy metal-associated isoprenylated plant proteins (HIPPs) are a metallochaperone-like protein family comprising a combination of structural features unique to vascular plants. HIPPs possess both one or two heavy metal-binding domains and an isoprenylation site, facilitating a posttranslational protein lipid modification. Recent work has characterized individual HIPPs across numerous different species and provided evidence for varied functionalities. Interestingly, a significant number of HIPPs have been identified in proteomes of plasmodesmata (PD)-nanochannels mediating symplastic connectivity within plant tissues that play pivotal roles in intercellular communication during plant development as well as responses to biotic and abiotic stress. As characterized functions of many HIPPs are linked to stress responses, plasmodesmal HIPP proteins are potentially interesting candidate components of signaling events at or for the regulation of PD. Here, we review what is known about PD-localized HIPP proteins specifically, and how the structure and function of HIPPs more generally could link to known properties and regulation of PD.

Identification of a new QTL underlying seminal root number in a maize-teosinte population

Seminal roots play an important role in acquisition of water and nutrients by maize seedlings. Compared with its teosinte ancestor, maize underwent a change in seminal root number (SRN). Although several key genes controlling SRN have been cloned, identification and utilization of new genes from teosinte would be useful for improving maize root architecture. In this study, a maize-teosinte BC₂F₆ population containing 206 individuals genotyped by resequencing was used to conduct high-resolution quantitative trait locus (QTL) mapping of SRN. A new major QTL on chromosome 7 (qSRN7) was identified. Differentially expressed genes (DEGs) based on RNA-Seq were identified between two inbred lines with no SRN and multiple SRN at two periods of seminal roots primordia formation. A total of 116 DEGs detected in at least one period were identified within the qSRN7 interval. Three DEGs (Zm00001d021572, Zm00001d021579 and Zm00001d021861) associated with SRN were identified through regional association mapping. When compared with reported domestication-related selective sweeps, Zm00001d021572 was selected during maize domestication. Our findings provide important insights into the genetic basis of SRN and identify a promising candidate gene for further studies on SRN.

(Don't) Look Up!: Is short-root just a short-root plant?

SHORT-ROOT (SHR) is a mobile transcription factor that plays important roles in ground tissue patterning, stem cell niche specification and maintenance, and vascular development in Arabidopsis roots. Although mRNA and protein of SHR are also found in hypocotyls, inflorescence stems, and leaves, its role in the above-ground organs has been less explored. In most developmental cases, SHR, together with its partner SCARECROW (SCR), regulates the expression of downstream target genes in controlling formative and proliferative cell divisions. Accumulating evidence on the regulatory role of SHR in shoots suggests that SHR may also play key roles in the above-ground organs. Interestingly, recent work has provided new evidence that SHR is also required for cell elongation in the hypocotyl of the etiolated seedling. This suggests that the novel roles of SHR and SHR-mediated regulatory networks can be found in shoots. Furthermore, comparative research on SHR function in roots and shoots will broaden and deepen our understanding of plant growth and development.