Required for the promotion of megasporogenesis, or promotion of germ cell formation from somatic precursor cells. Acts redundantly with WIH2. Functions in a genetic pathway downstream of SPL/NZZ and WUS and together with TRN2 in promoting megasporogenesis (PubMed:21658947). Involved in resistance to abiotic stress (PubMed:29272523). Homodimer and heterodimers (PubMed:29272523). Interacts with CYSTM7, CYTSM3, CYTSM4, CYTSM5, CYTSM6, CYTSM9, CYTSM10 and CYTSM11 (PubMed:29272523). Binds weakly to CYSTM1 and CYSTM2 (PubMed:29272523). Expressed in root meristem, root vasculature, leaf vasculature and floral organ primordia (PubMed:21658947). Mostly expressed in roots and flowers and, to a lower extent, in stems, siliques and leaves (PubMed:29272523). During ovule development, expressed in the nucellus from early stage until embryo sac maturity. Induced by heat in roots. No visible phenotype under normal growth conditions, but flowers of the double mutants wih1-1 and wih2-1 have defect in megasporgogenesis. Doubl mutant plants display retarded growth, and twisted leaves, siliques and roots. Belongs to the CYSTM1 family.