# Role of callose accumulation in the suppression of calcium-deficiency-induced necrosis in Arabidopsis thaliana cotyledons

## TL;DR

This study shows that callose limits the spread of cell death in Arabidopsis under low calcium conditions, but does not prevent its start.

## Contribution

The paper reveals that callose suppresses the propagation, not initiation, of calcium-deficiency-induced necrosis.

## Key findings

- The gsl10 mutant had larger necrotic spots compared to wild-type plants under low-Ca conditions.
- Callose accumulation limits the spread of cell death, leading to a distinct necrotic pattern at the cotyledon tip.
- The initiation of cell death is not suppressed by callose, but its propagation is.

## Abstract

Calcium (Ca) deficiency symptoms, such as blossom end rot in tomato and tip burn in lettuce, are among the most serious physiological disorders in agriculture. A common feature of this disorder is the expansion of necrosis. However, mechanisms underlying Ca-deficiency-induced necrosis remain poorly understood. We previously identified callose synthase genes (GSL1, GSL8, GSL10) as the causal genes of low-Ca-sensitive Arabidopsis thaliana mutants, which exhibit severe cell death in true leaves and reduced callose accumulation in cotyledons under low-Ca conditions. This raises the question of whether callose accumulation suppresses the spread of cell death. To clarify their relationship within the same organ, we examined callose deposition and cell death in the cotyledons of the gsl10 mutant. Although the gsl10 mutant showed a comparable level of total cell death to wild-type plants, the necrotic spots were larger. Furthermore, the largest necrotic spots were typically found at the cotyledon tip, but this tendency was weaker in gsl10 mutant. Collectively, our results suggest that callose does not suppress the initiation of cell death but rather limits its propagation, thereby leading to the formation of a characteristic necrotic pattern preferentially occurring at the cotyledon tip.