Downregulation of chloroplast protease AtDeg5 leads to changes in chronological progression of ontogenetic stages, leaf morphology and chloroplast ultrastructure in Arabidopsis

Abstract

The chloroplast protein AtDeg5 is a serine-type protease peripherally attached to thylakoid membrane at its lumenal side. Since reliable data regarding the role of AtDeg5 in controlling the course of growth and developmental processes are extremely limited, two independent T-DNA insertional lines with different extent of AtDeg5 reduction were prepared and ontogenesis stage-based analysis performed. Both mutant lines displayed a compensatory overaccumulation of AtDeg8. The repression of AtDeg5 protease altered a range of phenotypic features in at least one of the mutants, with the most prominent being changes in chronological progression of development and growth of individual rosette leaves, flower production and silique ripening as well as in the area of fully expanded leaves and chloroplast ultrastructure. By analyzing the results of parallel-mutant screening we conclude that AtDeg8 overdose may rescue 23% of AtDeg5 deficiency with regard to some AtDeg5-controlled traits; alternatively AtDeg5 may have catalytic sites in excess so that these traits might remain unaltered when AtDeg5 pool is reduced by 23%. For some other AtDeg5-dependent traits the absence of excessive amount of AtDeg5 catalytic sites, lack of AtDeg5 dosage effect and inability of AtDeg8 to compensate deficiency or absence of AtDeg5 occurred.

Chloroplast protease/chaperone AtDeg2 influences cotyledons opening and reproductive development in Arabidopsis

“…2), we suggest that AtDeg2 regulates the turnover of a chloroplast protein that has a functional link with flowering repressors and/or promoters turnover. Other AtDeg proteases may have similar function as suggested by the ability of AtDeg5 to regulate flower production (secondary Stage 6.5 of ontogenesis) [11].…”

“…We previously reported that AtDeg2 controls the area of juvenile leaves but does not impact the area of mature rosette leaves of 4-week-old plants [9], i.e., when mature leaves were still growing but juvenile leaves have finished their expansion [11]. We now wanted to know whether the fully expanded mature leaves follow the same trend.…”

“…Our results show that both the protease and chaperone activities of AtDeg2 are necessary for cotyledon opening and plant generative development to proceed correctly under nonstress growth conditions. -GFP 4.31 were sown on sphagnum peat moss and wood pulp (Agro Wit, Poland) and grown under long-day conditions in an identical manner as described previously [11].…”

“…Theses stages are leaf development (Stage 1), inflorescence emergence (Stage 5), flower production (Stage 6), and silique ripening (Stage 8) [11]. The rosette growth (principal Stage 3) was analyzed as described [15].…”

The contribution of individual domains of chloroplast protein AtDeg2 to its chaperone and proteolytic activities

“…Little is known about the physiological significance of chloroplast-targeted AtDegs, and AtDeg2 in particular under nonstressing conditions. AtDeg5 was shown in this respect to be involved in regulation of chronological progression of ontogenetic stages, leaf morphology, and chloroplast ultrastructure [18] and AtDeg2 was demonstrated to be required for morphology and ontogenesis of chloroplasts in juvenile rosette leaves [16].…”