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bioRxiv · 10.1101/2023.11.05.565727

The Arabidopsis katamari2 Mutant Exhibits a Hypersensitive Seedling Arrest Response at the Phase Transition from Heterotrophic to Autotrophic Growth

Hosokawa, C.·Yagi, H.·Segami, S.·Nagano, A. J.·Koumoto, Y.·Tamura, K.·Oka, Y.·Matsushita, T.·Shimada, T.
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Abstract

Young seedlings use nutrients stored in the seeds to grow and acquire photosynthetic potential. This process, called seedling establishment, involves a developmental phase transition from heterotrophic to autotrophic growth. Some membrane-trafficking mutants of Arabidopsis thaliana (Arabidopsis), such as the katamari2 (kam2) mutant, exhibit growth arrest during seedling development, with a portion of individuals failing to develop true leaves on sucrose-free solid medium. However, the reason for this seedling arrest is unclear. In this study, we show that seedling arrest is a temporal growth arrest response that occurs not only in kam2 but also in wild-type Arabidopsis; however, the threshold for this response is lower in kam2 than in the wild type. A subset of the arrested kam2 seedlings resumed growth after transfer to fresh sucrose-free medium. Growth arrest in kam2 on sucrose-free medium was restored by increasing the gel concentration of the medium or covering the surface of the medium with a perforated plastic sheet. Wild-type Arabidopsis seedlings were also arrested when the gel concentration of sucrose-free medium was reduced. RNA sequencing revealed that transcriptomic changes associated with the rate of seedling establishment were observed as early as 4 days after sowing. Our results suggest that the growth arrest of both kam2 and wild-type seedlings is an adaptive stress response and is not simply caused by the lack of a carbon source in the medium. This study provides a new perspective on an environmental stress response under unfavorable conditions during the phase transition from heterotrophic to autotrophic growth in Arabidopsis.

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Hosokawa, C., Yagi, H., Segami, S., Nagano, A. J., Koumoto, Y., Tamura, K., Oka, Y., Matsushita, T., Shimada, T.. 2023-11-06. The Arabidopsis katamari2 Mutant Exhibits a Hypersensitive Seedling Arrest Response at the Phase Transition from Heterotrophic to Autotrophic Growth. https://doi.org/10.1101/2023.11.05.565727

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