Regulatory Mechanisms of Shoot Branching in Plants

Shoot branching is governed by a complex interplay of hormonal signals, transcriptional regulators and environmental cues that together determine the fate of axillary buds. Central to this process is the concept of apical dominance, whereby auxin produced at the shoot apex moves basipetally down the stem to suppress the outgrowth of lateral buds. Cytokinins counteract this inhibition by promoting bud activation, while strigolactones reinforce apical dominance through modulation of auxin transport and direct suppression of bud outgrowth. Gibberellins and abscisic acid further refine bud activity, contributing to species-specific patterns of branching in both annual and perennial plants. Key transcription factors such as BRANCHED1 integrate these hormonal inputs and environmental signals—light quality, nutrient status and carbohydrate availability—to orchestrate local gene regulatory networks that establish dormancy or trigger bud growth. Polar auxin transport streams and feedback loops govern competition among shoot apices for access to the common auxin transport pathway, enabling plants to adjust architecture in response to shading or resource limitation. Emerging evidence highlights mobile proteins and RNAs as systemic signals that link distal organs and ensure whole-plant coordination of branching patterns. The manipulation of these regulatory mechanisms holds promise for optimising crop yield, reducing labour in horticultural systems and adapting plant architecture to changing climates.

Research from Nature Portfolio

Recent studies in bread wheat have identified a key regulator of tiller bud outgrowth encoded by a conserved ankyrin repeat protein. A single amino acid substitution in this protein leads to elevated abscisic acid biosynthesis at the shoot base and enhanced signalling within axillary buds, resulting in reduced tiller number. Functional characterisation revealed that the wild-type protein interacts directly with an ABA receptor to suppress hormone signalling, thereby promoting tiller formation under favourable conditions. In rice, foundational work has elucidated how gibberellin-induced degradation of the DELLA protein SLR1 simultaneously triggers loss of the tiller number regulator MOC1. This dual degradation event explains the inverse relationship between plant height and tiller number: high gibberellin levels lead to stem elongation but reduce branching, while stabilisation of SLR1 preserves MOC1 and promotes the development of lateral shoots. Together, these studies define molecular links between major phytohormones and crop-relevant architecture traits.

Regulatory Mechanisms of Shoot Branching in Plants publication trend

The graph below shows the total number of articles in regulatory mechanisms of shoot branching in plants across all publications each year (not limited to Nature Index journals).

Technical terms

Apical dominance: Suppression of axillary bud outgrowth by auxin produced at the shoot apex.

Axillary bud: A meristematic structure positioned in the leaf axil that can develop into a branch or remain dormant.

Polar auxin transport: Directional movement of the plant hormone auxin through coordinated activity of PIN-type efflux carriers.

Strigolactone: A class of phytohormones that suppress lateral bud growth and modulate auxin transport.

BRANCHED1 (BRC1): A TCP family transcription factor acting as a central integrator of branching signals in many plant species.

References

1. Multiple pathways regulate shoot branching. Frontiers in Plant Science (2015).
2. Shaping plant architecture. Frontiers in Plant Science (2015).
3. Tiller Number1 encodes an ankyrin repeat protein that controls tillering in bread wheat. Nature Communications (2023).
4. SLR1 inhibits MOC1 degradation to coordinate tiller number and plant height in rice. Nature Communications (2019).
5. HY5 functions as a systemic signal by integrating BRC1-dependent hormone signaling in tomato bud outgrowth. Proceedings of the National Academy of Sciences of the United States of America (2023).
6. A gene regulatory network critical for axillary bud dormancy directly controlled by Arabidopsis BRANCHED1. New Phytologist (2023).
7. The tomato WRKY-B transcription factor modulates lateral branching by targeting BLIND, PIN4, and IAA15. Horticulture Research (2024).