Abstract
Embryogenesis is a critical developmental process that establishes the body organization of higher plants. During this process, the biogenesis of chloroplasts from proplastids is essential. A failure in chloroplast development during embryogenesis can cause morphologically abnormal embryos or embryonic lethality. In this study, we isolated a T-DNA insertion mutant of the Arabidopsis gene EMBRYO DEFECTIVE 2726 (EMB2726). Heterozygous emb2726 seedlings produced about 25% albino seeds with embryos that displayed defects at the 32-cell stage and that arrested development at the late globular stage. EMB2726 protein was localized in chloroplasts and was expressed at all stages of development, such as embryogenesis. Moreover, the two translation elongation factor Ts domains within the protein were critical for its function. Transmission electron microscopy revealed that the cells in emb2726 embryos contained undifferentiated proplastids and that the expression of plastid genome-encoded photosynthesis-related genes was dramatically reduced. Expression studies of DR5:GFP, pDRN:DRN-GFP, and pPIN1:PIN1-GFP reporter lines indicated normal auxin biosynthesis but altered polar auxin transport. The expression of pSHR:SHR-GFP and pSCR:SCR-GFP confirmed that procambium and ground tissue precursors were lacking in emb2726 embryos. The results suggest that EMB2726 plays a critical role during Arabidopsis embryogenesis by affecting chloroplast development, possibly by affecting the translation process in plastids.
Highlights
Higher plant development is a complex process that begins with embryogenesis
Most photosynthesis-related mutants are capable of generating weak seedlings with albino cotyledon/leaves (Motohashi et al, 2001; Huang et al, 2009), and Liu et al (2017) showed that Arabidopsis embryos are still able to develop into mature seeds under light deprivation conditions, demonstrating that the photosynthetic ability of chloroplasts is not required for embryogenesis
Reciprocal crosses of emb2726-4/+ with WT plants revealed no significant defects in the transmission efficiencies of the female and male gametophytes, confirming that the lack of homozygous offspring from this mutant is due to a defect in embryogenesis (Supplementary Table 2)
Summary
Higher plant development is a complex process that begins with embryogenesis. In Arabidopsis, embryogenesis starts from the asymmetric division of a zygote to generate a large basal cell and a small apical cell (Bayer et al, 2017). Most photosynthesis-related mutants are capable of generating weak seedlings with albino cotyledon/leaves (Motohashi et al, 2001; Huang et al, 2009), and Liu et al (2017) showed that Arabidopsis embryos are still able to develop into mature seeds under light deprivation conditions, demonstrating that the photosynthetic ability of chloroplasts is not required for embryogenesis In addition to their photosynthetic functions, chloroplasts, and non-photosynthetic plastids are important sites for the synthesis of various biomolecules, such as amino acids, fatty acids, and precursors of several plant hormones (Hsu et al, 2010; Allorent et al, 2015), which are critical for maintaining plant growth and development. The results provided evidence supporting that EMB2726 functions as an EF-Ts during translation in plastids to regulate chloroplast biogenesis and embryo development
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
