| During leaf senescence, chloroplast proteins are degraded and amino acids are recycled. Previous research showed that the tobacco CND41 protease played a role in chloroplast protein degradation during senescence. In Arabidopsis , two CND41 orthologs, Al-2 (AtSgl 0760) and Al-3 (AtSg10770), display increased expression in older leaves. Individual al-2 and al-3 knockout Arabidopsis mutants did not show any delays in protein degradation during senescence. Therefore, in order to verify the function of the Al-2 and Al-3 genes, we knocked down Al-2 expression in an al-3 knockout mutant. Two mutant lines, 29 and 42, showed no differences in chloroplast protein degradation compared to the wildtype. Real-time qPCR showed the Al-2 mRNA level remained less than 10% in the mutant plants from early development through 8 weeks. However, Al-2 mRNA levels in 9-week mutant plants reached about 40% of wild type levels in both lines. This indicates RNAi efficiency was reduced in the most senescent leaves. Therefore, we cannot determine the role of Al-2 and Al-3 during leaf senescence due to the loss of RNAi efficiency in the senescent tissue. |
