DELLA proteins regulate spore germination and reproductive development in Physcomitrium patens

Abstract

Summary Proteins of the DELLA family integrate environmental signals to regulate growth and development throughout the plant kingdom. Plants expressing non‐degradable DELLA proteins underpinned the development of high‐yielding ‘Green Revolution’ dwarf crop varieties in the 1960s. In vascular plants, DELLAs are regulated by gibberellins, diterpenoid plant hormones. How DELLA protein function has changed during land plant evolution is not fully understood. We have examined the function and interactions of DELLA proteins in the moss Physcomitrium (Physcomitrella) patens, in the sister group of vascular plants (Bryophytes). PpDELLAs do not undergo the same regulation as flowering plant DELLAs. PpDELLAs are not degraded by diterpenes, do not interact with GID1 gibberellin receptor proteins and do not participate in responses to abiotic stress. PpDELLAs do share a function with vascular plant DELLAs during reproductive development. PpDELLAs also regulate spore germination. PpDELLAs interact with moss‐specific photoreceptors although a function for PpDELLAs in light responses was not detected. PpDELLAs likely act as ‘hubs’ for transcriptional regulation similarly to their homologues across the plant kingdom. Taken together, these data demonstrate that PpDELLA proteins share some biological functions with DELLAs in flowering plants, but other DELLA functions and regulation evolved independently in both plant lineages.

A DELAY OF GERMINATION 1 (DOG1)‐like protein regulates spore germination in the moss Physcomitrium patens

“…Since Ppdog1‐l1 , Ppdellaa , Ppdellab and Ppdellaab showed a similar germination phenotype (Phokas et al., 2023), we wondered whether Pp DOG1‐L1 protein could interact with Pp DELLAa and Pp DELLAb.…”

“…Therefore, we generated yeast vectors containing full‐length PpDOG1‐L1 coding sequences fused to a DNA‐binding domain (pGBKT7) and full‐length PpDELLA coding sequences fused to the GAL4 activation domain (pGADT7). Expression and subsequent translation of the proteins in yeast were detected via Western blot targeting the fused MYC tag (Figure S6a; Phokas et al., 2023). After introducing both plasmids into a Y2H reporter strain, we observed growth for all combinations on selective media without LEU and TRP , indicating that both plasmids were present in the yeast (Figure S6b).…”

“…The DOG1 domain of PpDOG1-L1 interacts in a yeast twohybrid (Y2H) assay with the PpDELLAa and PpDELLAb proteins Since Ppdog1-l1, Ppdellaa, Ppdellab and Ppdellaab showed a similar germination phenotype (Phokas et al, 2023), we wondered whether PpDOG1-L1 protein could interact with PpDELLAa and PpDELLAb.…”

“…Western blotting and yeast two hybrid including transformation of Matchmaker (AH109) yeast was performed as described in Bailey et al (2021) and Phokas et al (2023). Briefly, for yeast transformation, single colonies cultured on YPAD agar medium (20 g L À1 bacto-peptone, 10 g L À1 bacto-yeast extract, 20 g L À1 dextrose, 40 mg L À1 adenine sulfate, 20 g L À1 bacto-agar) were resuspended in 100 μl transformation buffer (2:1 50% PEG 3350MW, 1 M lithium acetate, 0.6% β-mercaptoethanol).…”

“…P. patens mutants that lack all diterpenoids show reduced spore germination (Vesty et al., 2016). Moreover, Pp DELLA proteins regulate spore germination, but this is independent of diterpenes (Phokas et al., 2023). Thus, the role and regulation of DOG1 and DELLA proteins in P. patens may be distinct from their role in seed plants.…”