nai1-1, ER body deficient mutant, vs wild-type Col-0

ER bodies are endoplasmic reticulum (ER)-derived organelles that might be involved in defense systems. The NAI1 gene regulates the development of ER bodies because mutation of NAI1 abolishes the formation of ER bodies. The nai1-1 mutant had a single nucleotide change at an intron acceptor site of At2g22770 (NAI1 gene). Because of this mutation, aberrant splicing of NAI1 mRNA occurs in the nai1-1 mutant. NAI1 encodes a transcription factor that has a basic-helix-loop-helix (bHLH) domain. Transient expression of NAI1 induced ER bodies in the nai1-1 mutant. To identify genes that are related to ER bodies, we compared the genome-wide expression profiles of Col-0 and the nai1-1 mutant using DNA microarrays. Twenty-nine genes were found to be expressed at least 2-fold more strongly in the nai1-1 mutant than in Col-0, and 341 genes were found to be expressed at least 2-fold more strongly in Col-0 than in the nai1-1 mutant. The 15 genes that showed the strongest expression in Col-0 compared to the expression in nai1-1 are shown in Table 1. Five of these genes are JAL genes (JAL22, JAL23, JAL31, JAL33 and PBP1/JAL30). The mRNA level of PYK10 was reduced in nai1-1 (4.3 fold larger in Col-0 than in nai1-1). The mRNA levels of GLL genes (GLL23 and GLL25) were also reduced in nai1-1. Keywords: mutant vs wt comparison Total RNA was purified from the roots of 20-day-old plants (3 plants were pooled for each genotype). Arabidopsis plants were grown under continuous light condition at 22˚C on MS medium paltes. The control plants and the nai1-1 mutant were cultivated in the same plate. This was done to avoid any difference in plant growth conditions between the mutants and the control plants.