The plant nuclear lamina disassembles to regulate genome folding in stress conditions

The nuclear lamina (NL) is a complex network of nuclear lamins and lamin-associated nuclear membrane proteins, which scaffold the nucleus to maintain structural integrity. In Arabidopsis thaliana, Nuclear Matrix Constituent Proteins (NMCPs) are essential components of the NL and are required to maintain the structural integrity of the nucleus and specific perinuclear chromatin anchoring. At the nuclear periphery, suppressed chromatin overlapping with repetitive sequences and inactive protein coding genes are enriched. At a chromosomal level, plant chromatin organization in interphase nuclei displays flexibilities in response to various developmental cues and environmental stimuli. Based on these observations in Arabidopsis, and given the role of AtNMCP genes (CRWN1 and CRWN4) in organizing chromatin positioning at the nuclear periphery, one can expect considerable changes in chromatin-NL interactions when the global chromatin organization patterns are being altered in plants. Here, we report the highly flexible nature of plant nuclear lamina, which disassembles substantially under various stress conditions. Particularly, under heat stress, we reveal that chromatin domains, initially tethered to the nuclear envelope, remain largely associated with CRWN1 and become scattered in the inner nuclear space. Via investigating the three-dimensional chromatin contact network, we further reveal that CRWN1 proteins play a structural role in shaping the changes in genome folding under heat stress. Also, CRWN1 acts as a negative transcriptional co-regulator to modulate the shift of the plant transcriptome profile in response to heat stress.