[Effects of chitosan on chloroplast protein of vegetable soybean under NaCl stress]

Chitosan (CTS) can effectively enhance the tolerance of plants to salt stress, but its role in driving the responses of vegetable soybean seedlings to salt stress at proteomic level is still unclear. Here, both 200 mmol·L-1 CTS and distilled water were used to spray the leaves of vegetable soybean 'Lvlingtezao' seedlings. After 5 days of induction, NaCl stress and nutrient solution without NaCl were treated. Chloroplast proteins were extracted from leaves on the third day of NaCl treatment and analyzed by using the isobaric tags for relative and absolute quantification (iTRAQ). The result showed that CTS significantly increased net photosynthetic rate (Pn) of vegetable soybean seedlings under NaCl stress. Totally 549 reliable quantitative information proteins were identified, of which 442 existed in at least two biological repeats, including 26 up-regulated proteins and 4 down-regulated proteins associated with the effects of CTS on vegetable soybean response to NaCl stress. In addition, enrichment analysis of molecular function and metabolic pathway showed that up-regulated proteins were mainly related to molecular functions, including electron transport, chlorophyll binding, electron carrier activity, and were enriched in the pathways of photoreaction, carbon reaction and glyoxylic acid and dicarboxylic acid metabolism. Down-regulated proteins were mainly related to poly (U) RNA binding. Our results suggested that CTS could affect photosynthesis of vegetable soybean seedlings under NaCl stress through multiple pathways.

In Silico Analysis of ACE Inhibitory Peptides from Chloroplast Proteins of Red Alga Grateloupia asiatica

Inhibition of angiotensin I-converting enzyme (ACE) is one of the key factors to repress high blood pressure. Although many studies have been reported that seaweed protein hydrolysates showed the ACE inhibitory activity, the comprehensive understanding of the relationship was still unclear. In this study, we employed chloroplast genome for in silico analysis and compared it with in vitro experiments. We first extracted water-soluble proteins (WSP) from red alga Grateloupia asiatica, which contained mainly PE, PC, APC, and Rbc, and prepared WSP hydrolysate by thermolysin, resulting that the hydrolysate showed ACE inhibitory activity. Then, we determined the complete chloroplast genome of G. asiatica (187,518 bp: 206 protein-coding genes, 29 tRNA, and 3 rRNA) and clarified the amino acid sequences of main WSP, i.e., phycobiliproteins and Rubisco, to perform in silico analysis. Consequently, 190 potential ACE inhibitory peptides existed in the main WSP sequences, and 21 peptides were obtained by in silico thermolysin digestion. By comparing in vitro and in silico analyses, in vitro ACE inhibitory activity was correlated to the IC₅₀ value from in silico digestion. Therefore, in silico approach provides insight into the comprehensive understanding of the potential bioactive peptides from seaweed proteins.

Nucleus- and plastid-targeted annexin 5 promotes reproductive development in Arabidopsis and is essential for pollen and embryo formation

BACKGROUND

Pollen development is a strictly controlled post-meiotic process during which microspores differentiate into microgametophytes and profound structural and functional changes occur in organelles. Annexin 5 is a calcium- and lipid-binding protein that is highly expressed in pollen grains and regulates pollen development and physiology. To gain further insights into the role of ANN5 in Arabidopsis development, we performed detailed phenotypic characterization of Arabidopsis plants with modified ANN5 levels. In addition, interaction partners and subcellular localization of ANN5 were analyzed to investigate potential functions of ANN5 at cellular level.

RESULTS

Here, we report that RNAi-mediated suppression of ANN5 results in formation of smaller pollen grains, enhanced pollen lethality, and delayed pollen tube growth. ANN5 RNAi knockdown plants also displayed aberrant development during the transition from the vegetative to generative phase and during embryogenesis, reflected by delayed bolting time and reduced embryo size, respectively. At the subcellular level, ANN5 was delivered to the nucleus, nucleolus, and cytoplasm, and was frequently localized in plastid nucleoids, suggesting a likely role in interorganellar communication. Furthermore, ANN5-YFP co-immunoprecipitated with RABE1b, a putative GTPase, and interaction in planta was confirmed in plastidial nucleoids using FLIM-FRET analysis.

CONCLUSIONS

Our findings let us to propose that ANN5 influences basal cell homeostasis via modulation of plastid activity during pollen maturation. We hypothesize that the role of ANN5 is to orchestrate the plastidial and nuclear genome activities via protein-protein interactions however not only in maturing pollen but also during the transition from the vegetative to the generative growth and seed development.