# CLAVATA3 Signaling Buffers Arabidopsis Shoot Apical Meristem Activity in Response to Photoperiod

## TL;DR

This study shows how CLAVATA3 signaling in Arabidopsis regulates plant growth in response to changes in day length.

## Contribution

The study reveals that CLV3 signaling limits meristem activity in both long and short days, with a stronger effect in short days.

## Key findings

- CLV3 signaling restricts shoot apical meristem activity in both long-day and short-day conditions.
- clv3 mutants produce more leaves and larger inflorescence meristems compared to wild-type plants.
- CLV3 signaling plays a more prominent role in regulating meristem activity during short days.

## Abstract

Land plants grow throughout their life cycle via the continuous activity of stem cell reservoirs contained within their apical meristems. The shoot apical meristem (SAM) of Arabidopsis and other land plants responds to a variety of environmental cues, yet little is known about the response of meristems to seasonal changes in day length, or photoperiod. Here, the vegetative and reproductive growth of Arabidopsis wild-type and clavata3 (clv3) plants in different photoperiod conditions was analyzed. It was found that SAM size in wild-type Arabidopsis plants grown in long-day (LD) conditions gradually increased from embryonic to reproductive development. clv3 plants produced significantly more leaves as well as larger inflorescence meristems and more floral buds than wild-type plants in LD and short-day (SD) conditions, demonstrating that CLV3 signaling limits vegetative and inflorescence meristem activity in both photoperiods. The clv3 phenotypes were more severe in SDs, indicating a greater requirement for CLV3 restriction of SAM function when the days are short. In contrast, clv3 floral meristem size and carpel number were unchanged between LD and SD conditions, which shows that the photoperiod does not affect the regulation of floral meristem activity through the CLV3 pathway. This study reveals that CLV3 signaling specifically restricts vegetative and inflorescence meristem activity in both LD and SD photoperiods but plays a more prominent role during short days.