Grant, D. G. | Search bioRxiv

bioRxiv2021

Maize Brittle Stalk2-Like3, encoding a COBRA protein, functions in cell wall formation and carbohydrate partitioning

Carbohydrate partitioning from leaves to sink tissues is essential for plant growth and development. The maize (Zea mays) recessive carbohydrate partitioning defective28 (cpd28) and cpd47 mutants exhibit leaf chlorosis and accumulation of starch and soluble sugars. Transport studies with 14C-sucrose (Suc) found drastically decreased export from mature leaves in cpd28 and cpd47 mutants relative to wild-type siblings. Consistent with decreased Suc export, cpd28 mutants exhibited decreased phloem pressure in mature leaves, and altered phloem cell wall ultrastructure in immature and mature leaves. We identified the causative mutations in the Brittle Stalk2-Like3 (BK2L3) gene, a member of the COBRA family, which is involved in cell wall development across angiosperms. None of the previously characterized COBRA genes are reported to affect carbohydrate export. Consistent with other characterized COBRA members, the BK2L3 protein localized to the plasma membrane, and the mutants condition a dwarf phenotype in dark-grown shoots and primary roots, as well as the loss of anisotropic cell elongation in the root elongation zone. Likewise, both mutants exhibit a significant cellulose deficiency in mature leaves. Therefore, BK2L3 functions in tissue growth and cell wall development, and this work elucidates a unique connection between cellulose deposition in the phloem and whole-plant carbohydrate partitioning. Funding InformationThe research was supported by US National Science Foundation Plant Genome Research Program grants (IOS-1025976 and IOS-1444448) to DMB.

genetics↗

bioRxiv2020

Plasmodesmata-localized proteins and reactive oxygen species orchestrate light-induced rapid systemic signaling in Arabidopsis

Systemic signaling and systemic acquired acclimation (SAA) are key to the survival of plants during episodes of abiotic stress. These processes depend on a continuous chain of cell-to-cell signaling events that extends from the initial tissue that senses the stress (local tissue) to the entire plant (systemic tissues). Among the different systemic signaling molecules and processes thought to be involved in this cell-to-cell signaling mechanism are reactive oxygen species (ROS), calcium, electric and hydraulic signals. How these different signals and processes are interlinked, and how they transmit the systemic signal all the way from the local tissue to the entire plant, remain however largely unknown. Here, studying the systemic response of Arabidopsis thaliana to a local treatment of excess light stress, we report that respiratory burst oxidase homolog D (RBOHD)-generated ROS enhance cell-to-cell transport and plasmodesmata (PD) pore size in a process that depends on the function of PD-localized proteins (PDLPs) 1 and 5, promoting the cell-to-cell transport of systemic signals during responses to light stress. We further identify aquaporins, and several different calcium-permeable channels, belonging to the glutamate receptor-like, mechanosensitive small conductance-like, and cyclic nucleotide-gated families, as involved in this process, but determine that their function is primarily required for the maintenance of the signal in each cell along the path of the systemic signal, as well as for the establishment of acclimation at the local and systemic tissues. PD and RBOHD-generated ROS orchestrate therefore light stress-induced rapid cell-to-cell spread of systemic signals in Arabidopsis. One-sentence summaryRespiratory burst oxidase homolog D-generated reactive oxygen species enhance cell-to-cell transport and plasmodesmata (PD) pore size in a process that depends on the function of the PD-localized proteins (PDLPs) 1 and 5, promoting the cell-to-cell transport of rapid systemic signals during the response of Arabidopsis to excess light stress.

plant biology↗