IGT/LAZY genes are differentially influenced by light and required for light-induced change to organ angle

Branching angles in the modulation of plant architecture: Molecular mechanisms, dynamic regulation, and evolution

Plants develop branches to expand areas for assimilation and reproduction. Branching angles coordinate with branching types, creating diverse plant shapes that are adapted to various environments. Two types of branching angle-the angle between shoots and the angle in relation to gravity or the gravitropic set-point angle (GSA) along shoots-determine the spacing between shoots and the shape of the aboveground plant parts. However, it remains unclear how these branching angles are modulated throughout shoot development and how they interact with other factors that contribute to plant architecture. In this review, we systematically focus on the molecular mechanisms that regulate branching angles across various species, including gravitropism, anti-gravitropic offset, phototropism, and other regulatory factors, which collectively highlight comprehensive mechanisms centered on auxin. We also discuss the dynamics of branching angles during development and their relationships with branching number, stress resistance, and crop yield. Finally, we provide an evolutionary perspective on the conserved role of auxin in the regulation of branching angles.

The transcription factor NF-YA10 determines the area explored by Arabidopsis thaliana roots and directly regulates LAZY genes

Root developmental plasticity relies on transcriptional reprogramming, which largely depends on the activity of transcription factors (TFs). NF-YA2 and NF-YA10 (nuclear factor A2 and A10) are downregulated by the specific miRNA isoform miR169defg. Here, we analyzed the role of the Arabidopsis thaliana TF NF-YA10 in the regulation of lateral root (LR) development. Plants expressing a version of NF-YA10 resistant to miR169 cleavage showed a perturbation in the LR gravitropic response. By extracting several features of root architecture using an improved version of the ChronoRoot deep-learning-based phenotyping system, we uncovered that these plants showed a differential angle of LRs over time when compared to Col-0. Detailed phenotyping of root growth dynamics revealed that NF-YA10 misregulation modulates the area explored by Arabidopsis roots. Furthermore, we found that NF-YA10 directly regulates LAZY genes, which were previously linked to gravitropism, by targeting their promoter regions. Hence, the TF NF-YA10 is a new element in the control of LR bending and root system architecture.

Peach ( Prunus persica ) TAC1 protein interaction with a LIGHT HARVESTING CHLOROPHYLL A/B BINDING (LHCB) homolog and transcriptomic analyses reveal connections to photosynthesis

Plants receive and interpret external light, gravity, and temperature cues to both set and change the angles of their lateral organs for optimal growth and development. In recent years, the roles of the IGT/LAZY protein family in integrating light and gravity cues have become increasingly apparent. Here we investigated protein-protein interactions for peach ( Prunus persica ) TAC1 (PpeTAC1). TAC1 is a light-regulated IGT/LAZY family member involved in maintaining outward growth of lateral branches in numerous plant species. Using a yeast-two-hybrid screen with a peach library, we identified three candidate protein interactors, including a LIGHT HARVESTING CHLOROPHYLL A/B BINDING (LHCB) family protein. We found that neither TAC1 silencing nor PpeTAC1 overexpression in plum ( P. domestica ) altered chlorophyll content, despite a recent finding that LAZY1 -silenced plum trees have chlorotic leaves due to reduced chlorophyll. However, we identified multiple differentially expressed chloroplast-, photosynthesis-, and light-related genes between tac1 mutant and standard peaches. Collectively, we identified connections between PpeTAC1 and chloroplasts, photosynthesis-related machinery, and light. This data supports a role for the TAC1 protein as an integrator of light perception into mechanisms controlling lateral organ orientation in concert with or in parallel to the LAZY/DRO gravitropic-response pathway.

Light at the end of the tunnel: integrating signaling pathways in the coordination of lateral root development

Root system architecture (RSA) encompasses a range of physical root attributes, including the lateral roots (LRs), root hairs and adventitious roots, in addition to the primary or main root. This overall structure is a crucial trait for efficient water and mineral capture alongside providing anchorage to the plant in the soil and is vital for plant productivity and fitness. RSA dynamics are dependent upon various environmental cues such as light, soil pH, water, mineral nutrition and the belowground microbiome. Among these factors, light signaling through HY5 significantly influences the flexibility of RSA by controlling different signaling pathways that converge at photoreceptors-mediated signaling, also present in the 'hidden half'. Furthermore, several phytohormones also drive the formation and emergence of LRs and are critical to harmonize intra and extracellular stimuli in this regard. This review endeavors to elucidate the impact of these interactions on RSA, with particular emphasis on LR development and to enhance our understanding of the fundamental mechanisms governing the light-regulation of LR growth and physiology.

Genetic regulation of the root angle in cereals

The root angle plays a critical role in efficiently capturing nutrients and water from different soil layers. Steeper root angles enable access to mobile water and nitrogen from deeper soil layers, whereas shallow root angles facilitate the capture of immobile phosphorus from the topsoil. Thus, understanding the genetic regulation of the root angle is crucial for breeding crop varieties that can efficiently capture resources and enhance yield. Moreover, this understanding can contribute to developing varieties that effectively sequester carbon in deeper soil layers, supporting global carbon mitigation efforts. Here we review and consolidate significant recent discoveries regarding the molecular components controlling root angle in cereal crop species and outline the remaining research gaps in this field.