Abstract
ABSTRACT
Viral infection often induces chlorosis, a symptom closely associated with chlorophyll (Chl) degradation. STAY‐GREEN (SGR) proteins are key regulators of Chl breakdown, but their roles in plant virus resistance remain poorly understood. In this study, we identified six
NtSGR
family genes in
Nicotiana tabacum
and functionally characterized
NtSGRL1
during tomato yellow leaf curl virus (TYLCV) infection. TYLCV drastically upregulates
NtSGRL1
(149‐fold at 4 days post‐inoculation [dpi] vs. control), suggesting its involvement in the tobacco–TYLCV interaction. Subcellular localization revealed that NtSGRL1 is targeted to both the nucleus and chloroplast, and yeast assays confirmed its transcriptional activation activity, indicating potential dual functions. TYLCV accumulation was reduced by 1995‐fold in
Ntsgrl1
mutants relative to wild‐type (WT) plants at 10 dpi. Further assays with tomato spotted wilt virus (TSWV), potato virus Y (PVY) and tobacco mosaic virus (TMV) showed that viral accumulation in
Ntsgrl1
mutants was reduced by 62%–99%, suggesting that NtSGRL1 may affect resistance to additional tested viruses. Transcriptomics revealed 1470 differentially expressed genes in TYLCV‐infected
Ntsgrl1
plants enriched in MAPK signalling and phenylpropanoid biosynthesis pathways. Virus‐induced gene silencing (VIGS)‐based validation further supported the involvement of these pathways in TYLCV resistance. Overall, this study identifies
NtSGRL1
as a critical regulator of antiviral resistance in tobacco and reveals its dual functional roles as both a Chl‐related enzyme and a transcriptional regulator. These findings provide new insights into plant antiviral mechanisms and potential genetic resources for breeding virus‐resistant crops.