The molecular bases of responses to light excess in photosynthetic organismshaving different evolutionary histories and belonging to different lineages are still not completely characterized.Therefore I explored the functions of photoprotective antennae in green algae, mosses and diatoms, together withthe role of the two xanthophyll cycles present in diatoms.I studied the Light Harvesting Complex Stress-Related (LHCSR) proteins in different organisms. In thegreen alga Chlamydomonas reinhardtii, LHCSR3 is a protein important for photoprotection. I used site-specificmutagenesis in vivo and in vitro and identified three residues of LHCSR3 that are responsible for its activation.With the moss Physcomitrella patens I studied the in vitro spectroscopic and quenching characteristics ofdifferent pigment-binding mutants of the protein LHCSR1, focusing in particular on chlorophylls A2 and A5.LHCSRs in diatoms are named LHCXs, and in Phaeodactylum tricornutum I found that multiple abioticstress signals converge to regulate the LHCX content of cells, providing a way to fine-tune light harvesting andphotoprotection.The other main driver of photoprotection in diatoms is the xanthophyll cycle. Here I found that the accu-mulation of viola- and zeaxanthin in P. tricornutum have a negative effect in the development of NPQ, showingthat zeaxanthin does not participate in the enhancing of NPQ in diatoms.Thanks to these studies done on different organisms, we gained a deeper knowledge on the shared character-istics and on the peculiar features about photoprotection in green algae, mosses and diatoms.
|Titolo:||Light Stress and Photoprotection in Green algae, Mosses and Diatoms|
|Data di pubblicazione:||2016|
|Appare nelle tipologie:||07.13 Doctoral Thesis|