Early leaf senescence can cause negative effects on rice yield and its
regulation is relatively unknown. The team of Dong-Dong Zeng from Zhejiang
University in China isolated and studied the bilateral blade senescence 1
(bbs1) rice (Oryza sativa), an early leaf senescence mutant with a premature
senescence phenotype that occurs at the leaf margins, in hopes of
understanding the mechanism of early leaf senescence.
The mutant showed premature leaf senescence beginning at the tillering stage
and exhibited severe symptoms at the late grain-filling stage. The mutant
also showed accelerated dark-induced leaf senescence. The OsBBS1 gene of the
bbs1 mutant was analyzed and was found to have an insertion in its first
exon. This gene encodes a receptor-like cytoplasmic kinase.
OsBBS1-knockout plants generated via CRISPR-Cas9 exhibited similar early
leaf senescence phenotypes as did the bbs1 mutant. The OsBBS1 gene is
expressed in all detected tissues and was predominantly expressed in the
main vein region of mature leaves. The expression of OsBBS1 could be greatly
induced by salt stress, and the bbs1 mutant exhibited hypersensitivity to
This is the first identification of OsBBS1 being involved in leaf senescence
and playing critical roles in the salt stress response in rice.