Fungal Cell Wall-Associated Effectors: Sensing, Integration, Suppression, and Protection.

The cell wall (CW) of plant-interacting fungi, as the direct interface with host plants, plays a crucial role in fungal development. A number of secreted proteins are directly associated with the fungal CW, either through covalent or non-covalent interactions, and serve a range of important functions. In the context of plant-fungal interactions many are important for fungal development in the host environment and may therefore be considered fungal CW-associated effectors (CWAEs). Key CWAE functions include integrating chemical/physical signals to direct hyphal growth, interfering with plant immunity, and providing protection against plant defenses. In recent years, a diverse range of mechanisms have been reported that underpin their roles, with some CWAEs harboring conserved motifs or functional domains, while others are reported to have novel features. As such, the current understanding regarding fungal CWAEs is systematically presented here from the perspective of their biological functions in plant-fungal interactions. An overview of the fungal CW architecture and the mechanisms by which proteins are secreted, modified, and incorporated into the CW is first presented to provide context for their biological roles. Some CWAE functions are reported across a broad range of pathosystems or symbiotic/mutualistic associations. Prominent are the chitin interacting-effectors that facilitate fungal CW modification, protection, or suppression of host immune responses. However, several alternative functions are now reported and are presented and discussed. CWAEs can play diverse roles, some possibly unique to fungal lineages and others conserved across a broad range of plant-interacting fungi. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Development of ß-carotene, lysine, and tryptophan-rich maize (Zea mays) inbreds through marker-assisted gene pyramiding.

Maize (Zea mays L.) is the leading cereal crop and staple food in many parts of the world. This study aims to develop nutrient-rich maize genotypes by incorporating crtRB1 and o2 genes associated with increased ß-carotene, lysine, and tryptophan levels. UMI1200 and UMI1230, high quality maize inbreds, are well-adapted to tropical and semi-arid regions in India. However, they are deficient in ß-carotene, lysine, and tryptophan. We used the concurrent stepwise transfer of genes by marker-assisted backcross breeding (MABB) scheme to introgress crtRB1 and o2 genes. In each generation (from F1, BC1F1-BC3F1, and ICF1-ICF3), foreground and background selections were carried out using gene-linked (crtRB1 3'TE and umc1066) and genome-wide simple sequence repeats (SSR) markers. Four independent BC3F1 lines of UMI1200 × CE477 (Cross-1), UMI1200 × VQL1 (Cross-2), UMI1230 × CE477 (Cross-3), and UMI1230 × VQL1 (Cross-4) having crtRB1 and o2 genes and 87.45-88.41% of recurrent parent genome recovery (RPGR) were intercrossed to generate the ICF1-ICF3 generations. Further, these gene pyramided lines were examined for agronomic performance and the ß-carotene, lysine, and tryptophan contents. Six ICF3 lines (DBT-IC-ß1σ4-4-8-8, DBT-IC-ß1σ4-9-21-21, DBT-IC-ß1σ4-10-1-1, DBT-IC-ß2σ5-9-51-51, DBT-IC-ß2σ5-9-52-52 and DBT-IC-ß2σ5-9-53-53) possessing crtRB1 and o2 genes showed better agronomic performance (77.78-99.31% for DBT-IC-ß1σ4 population and 85.71-99.51% for DBT-IC-ß2σ5 population) like the recurrent parents and ß-carotene (14.21-14.35 µg/g for DBT-IC-ß1σ4 and 13.28-13.62 µg/g for DBT-IC-ß2σ5), lysine (0.31-0.33% for DBT-IC-ß1σ4 and 0.31-0.34% for DBT-IC-ß2σ5), and tryptophan (0.079-0.082% for DBT-IC-ß1σ4 and 0.078-0.083% for DBT-IC-ß2σ5) levels on par with that of the donor parents. In the future, these improved lines could be developed as a cultivar for various agro-climatic zones and also as good genetic materials for maize nutritional breeding programs.