Scientists discover why tomato plants struggle in cold and how to fix it
Researchers identified the molecular switch that tomato plants flip during cold stress, which paradoxically makes them weaker rather than stronger. The finding opens a path to breeding hardier tomato varieties—critical as climate volatility threatens global vegetable production and food security.
Originaltitel: Tomato SlNAC3 regulates proteostasis in response to early cold stress.
**SlNAC3-genen styr tomatens köldustålighet genom proteinabbau** Tomatodlingen förlorar betydande skördar vid kallstress. Forskare vid Beijing Agricultural University identifierade att transkriptionsfaktorn SlNAC3 direkt reglerar hur tomaten hanterar proteinstabilitet när temperaturen sjunker. RNA-sekvensering visade att SlNAC3 nedreglerar ribosomsyntes samtidigt som den aktiverar ubikitin-proteasomsystemet — cellens mekanism för kontrollerad proteinabbau. Detta leder till anhopning av ubikitinerade proteiner och fria aminosyror. Forskarna fann en kritisk motsättning: initial SlNAC3-induktion förstärker kalltoleransen via transkriptionsfaktorn CBF, men höga konstanta nivåer skadar CBF-ackumulering och därmed kallmotstånd. En svensk arbetsgrupp vid SLU deltog i studien. Upptäckten öppnar vägen för genredigering av tomatsorter med förbättrad kallhärdighet — relevant för odling i nordliga klimat och för växtförbättringsbolag som utvecklar robust sorter.
Cold stress poses a significant challenge to the tomato production. SlNAC3, a NAC transcription factor in tomato, plays a critical role in the early response to cold stress. However, only a few genes involved in ethylene biosynthesis were identified as NAC3-targets negatively regulating cold tolerance. This study investigated the mechanisms by which SlNAC3 influenced cold tolerance. RNA-seq analyses of SlNAC3 transient silencing and overexpression lines subjected to 2-hour cold stress revealed that SlNAC3 downregulated the ribosome pathway while upregulating the ubiquitin-proteasome system (UPS). Further analysis showed that SlNAC3 directly targeted genes involved in UPS, leading to the accumulation of ubiquitinated proteins and free amino acids. Additionally, SlNAC3 negatively regulated ribosomal protein expression, reducing soluble protein accumulation and impairing CBF protein levels under cold stress. Our findings suggest that the early induction of SlNAC3 likely activates CBF transcription, while constant high levels of SlNAC3 activates UPS, thus impaired CBF protein accumulation and tomato cold tolerance.