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Abstract
Dehydration-Responsive Element-Binding (DREB) transcription factors play an important role in plant responses to drought. DREB subfamily A4, contains a sub-group named TINY. Previous studies in Arabidopsis suggest that TINYs suppress plant growth and mediate abscisic acid (ABA)-induced stomatal closure. In this study, we investigated the function of the tomato drought-induced TINY1. Under drought conditions, tiny1 mutant lost turgor and wilted more rapidly than control M82 plants. However, this sensitivity was attributed to its larger leaf area, rather than intrinsic differences in drought response. Measurements of stomatal conductance, leaf temperature, and osmotic adjustment revealed no significant differences between tiny1 and M82. Furthermore, whole plant daily transpiration of M82 and tiny1 with similar leaf area, showed no differences. Interestingly, the growth-promoting effect of tiny1 was confined to early developmental stages; enhanced embryo growth and hypocotyl elongation, and accelerated emergence of the first true leaves—trait that later contributed to increased leaf area. At later stages, the mutation had no observable impact on growth rate. Our results show increased gibberellin (GA) activity in the mature tiny1 embryo and suggest that TINY1 suppresses embryonic growth by repressing GA biosynthesis through downregulation of GA 20-oxidase 4 (GA20ox4) gene expression.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Matar Azriel - matar.azriel{at}mail.huji.ac.il, Hagai Shohat- shohat{at}cshl.edu, Dalia Blinderman - dalia.blinderman{at}mail.huji.ac.il
Highlight- The tomato drought-induced DREB transcription factor TINY1 suppressed embryonic and early seedling growth by inhibiting gibberellin activity, but it had no significant effect on drought response mechanisms.
- Abbreviations
- DEG
- differentially expressed gene
- DREB
- Dehydration-Responsive Element-Binding
- RWC
- relative water content
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