# DBT JRF 2020 — Question 56

Exam: DBT JRF 2020 · Section: B · Topic: Plant Biology · Difficulty: Medium

## Question

Synthetic seeds are mostly derived from

## Options

- **A.** somatic embryos
- **B.** zygotic embryos
- **C.** fruit of coconut
- **D.** avocado seeds

## Answer

Option A

## Explanation

Glycosylation requires a complex membrane-bound machinery: glycosyltransferases that add specific sugar residues, sugar nucleotide transporters (to supply UDP-glucose, UDP-galactose, etc. into the ER lumen/Golgi), and chaperones for folding of glycoproteins. This entire apparatus is absent from plastids (chloroplasts, leucoplasts). Plastids CAN perform: Phosphorylation — via plastid-localised protein kinases and the photosynthetic machinery (e.g. thylakoid kinases STN7, STN8 phosphorylating LHCII proteins); Acetylation — of transit peptides and stroma enzymes; S-nitrosylation — by reactive nitrogen species in plastid stroma. Glycosylation of plastid proteins does NOT occur within the plastid — any glycoproteins imported into plastids are glycosylated in the ER before/during import.

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